Railway Lexicon


This lexicon was originally produced by the Railway Systems Group at the University of Sheffield in cooperation with Railtrack (now Network Rail) and other organisations. Staff at the University of Sheffield and the team of The Railway Consultancy update the Lexicon on a regular basis. In general, the UK term "railway" is used rather than the US term "railroad". Obsolete Railtrack terminology is shown in brackets where known. The tags at the end of phrases "RT" and "UoS" signify that Railtrack or the University of Sheffield, respectively, contributed the definition. Where definitions vary between sources or additional information is provided two definitions are provided. Comments and feedback are welcomed by: f.schmid@bham.ac.uk

Further information is available at:
The Modern Railway Glossary - The Brakes Glossary - The Steam Locomotive Glossary - The Electric Traction Glossary - Acronyms and Abbreviations - US-UK Terminology


Abnormal Heavy Road Load

Any road load which falls outside the scope of the Construction and Use Regulations because of its weight or weight distribution.RT

Abnormal Road Load Indemnity

A form of indemnity submitted to Network Rail by a road haulier as prescribed in the Motor Vehicles (Authorisation of Special Types) General Order 1979 (as amended).RT

Abnormal Road Load Notification

A notice submitted to Network Rail by a haulier which gives loading details of a proposed abnormal road load movement, its proposed date and time of travel, and its proposed route.RT

Absolute Block

A railway signalling system which is based on the principle of dividing a railway line into a sequence of individual sections or blocks, allied to the principle of never having more than one train on the same line in the same section at the same time.  The acceptance of a train by the signaller at the signal box in advance is necessary before a train is allowed to proceed into the Absolute Block Section.RT

Abstract of Particulars

A subsection of the contract conditions which contains routine details relevant to that specific contract.RT

Acceptable Quality Level

A value which limits the number of contract checks which are permitted to fail within a predetermined sample (e.g.  an AQL of 1.0 indicates that no more than 1.0% of the checks will be permitted to produce a fail without a tightening of the inspection regime.)RT

Acceptance (of rolling stock)

Final part of the process to introduce new types of rolling stock, onboard systems or infrastructure components to the railway network managed by Network Rail.UoS

Acceptance Manager

The Network Rail manager assigned by the RSAB Group Manager, having responsibility for managing the process for a route acceptance request.  The Acceptance Manager will be the Network Rail principal point of contact on noncommercial matters to the applicant.RT

Acceptance Plan

A Network Rail project plan defining Network Rail activities in support of a Route Acceptance Request.RT


UK railway signalling term, 'accepting' refers to the permission given by a signaller for a train to enter the section of line which he or she controls. UoS

Access Agreement

An agreement regulated under the Railways Act 1993 setting out the terms and conditions under which companies/operators obtain access to railway track, stations and certain types of depots.RT

Access Charge

The charge paid by railway operators for access to rail facilities which are the subject of an access agreement.RT

Access Planning Software

Access planning software system for the planning of track access for both permanent and shortterm train schedules.  It replaced PROTIM.RT


An unexpected, unplanned occurrence which results in physical harm (injury or disease) to an individual, damage to property, a near miss, a loss, or any combination of these effects.  (See also Incident.)RT+UoS

Accommodation Bridge

A bridge connecting two areas of land which were under common ownership but separated when the railway was built.RT

Account Executive

The manager responsible for commercial dealings with the Train Operators.RT

Accounts Payable

A team of people within the finance function responsible for the correct payment of authorised supplier invoices.RT

Account Receivable

A team of people within finance responsible for the dispatch and credit control of properly authorised invoices to customers.RT

Activity Based Costing

The process of identifying the costs associated with particular daytoday activities or specific tasks and projects.RT

Actual Costs

The term used to encompass both costs paid over to suppliers and accruals.RT

Actual Cost of Work Performed

An assessment of the physical progress on a scheme and its financial value.  This will include costs for invoices paid and accruals to repeat bills not yet presented for the actual progress achieved.RT

Add Value Machines

Used in some automatic fare collection systems to allow passengers to increase the residual value of a stored value ticket.UoS

Adhesion Coefficient (μ)

The ratio of the tangential and normal forces that exist between the wheel and the rail at standstill and during motion.  The adhesion coefficient for rolling motion is usually referred to as μ. Generally taken as 0.3 to 0.4 for dry rail, but can be as low as 0.01 for icy and greasy rail.UoS

Adjustment Switch

A device which allows longitudinal rail movement to dissipate thermal forces when CWR is adjacent to jointed track or other features not designed to withstand thermal forces.  Adjustment switches are also used when thermal forces, additional to those in CWR, may be encountered such as at long underbridges which are themselves subject to expansion and contraction.  (US term: Breather Switch.) RT

Advanced Passenger Train

High speed tilting train, abandoned in the early 1980s.RT

Air Rights Development

Property exceeding existing building height constructed on and above land owned by Network Rail.RT

Airless Spraying

The process of atomisation of paint by forcing it hydraulically through an orifice at high pressureRT


The horizontal (line) and vertical (top) position of a railway track, described by curved track of horizontal radius R, tangent track where R = ¥ , vertical radius and gradient.UoS

Alley (US)

A clear track in a switching yard.  (UK: marshalling yard.)UoS

Anchor Length

The length of CWR track that is left clipped down during the stressing operation to ensure that no movement occurs at the fixed ends of the length being stressed.RT

Ancillary Movement

Movements of locomotives and rolling stock directly in association with normal daytoday train services.RT

Annual Renewal Plan

Plan identifying those assets which were to be renewed by Railtrack in the forthcoming contract year..RT

AntiCreeper (US)

A device firmly attached to the base of a rail and bearing against a crosstie (sleeper), to keep the rail from moving longitudinally under traffic.  (UK: Rail Anchor.)UoS

Approved In Principle

Approval in principle signifies that a professionally competent person or body is satisfied that:

  • a scheme chosen to bring about a change to the infrastructure will meet the requirements of the remit; RT
  • appropriate standards and/or design criteria have been proposed for the design/checking phase.RT

Area Delivery Group

A zonal team charged with meeting the minutes delay targets by identifying, testing and implementing performance improvements.RT

Arm Repeater

An electrical indicator which shows the position of a semaphore signal arm to the controlling signalman.RT


The core feature of a rolling stock design where two adjacent railway vehicle ends are mounted on a common bogie.  Nowadays much favoured by tramcar or light rail vehicle designers.  Also used for some European highspeed train designs, namely, TGV and Eurostar carriages.  It has the benefit of reducing the number of bogies required for a train.  Generally only suitable for lighter weight vehicles since the load on each axle is proportionately increased.  Usually requires that special lifting systems or bogie drop pits are provided in maintenance workshops. UoS


The visual indication of a colour light (or mechanical) signal as displayed to the driver.RT

Asset Maintenance Plan

A plan of remedial maintenance work outstanding from the BR maintenance programme prior to creation of Railtrack.RT

Asset Maintenance Plan Provision

The funding provision provided to Railtrack on company formation to complete the works identified in the AMP.RT

Asset Management Work Team

The team which led a detailed review of Railtrack’s approach to asset management with the key objective of optimising maintenance and renewal costs.RT

Asset Related Expenditure

Any expenditure relating to the enhancement or renewal and, for certain asset categories, maintenance of the railway infrastructure and any other assets as per the Capital Accounting Rules.  This will include expenditure relating to Capital Enhancement and Renewal Projects, Asset Maintenance Plan and Station Regeneration Programme.  Refer to the Railtrack Investment Regulations, Capital Accounting Rules and SRP Financial Guidelines for further information.  RT

Asset Renewal

Replacement by Network Rail of an existing asset whose maintenance is within the scope of the RT1A contract.RT

Asset Replacement

Renewal of an asset undertaken by the contractor at no additional cost to the employer.RT

Associated Society of Locomotive Engineers and Firemen

Union, popularly known as ASLEF, which represents many train drivers.RT

Authority to Recruit

The approval, by a person with delegated authority, for the recruitment of permanent or agency staff.RT

Automatic Block Signal (ABS)

A train control subsystem based on a series of consecutive blocks governed by block signals which are controlled by the movement of trains and certain other conditions (e.g., detection of level crossing closure) rather than by a signaller or train describer driven route setting system.  The installation includes automatic line side signals, cab signals or both, actuated by a train or light engine by means of axle counters or track circuits.  This is a very basic form of automatic route setting (ARS).UoS

Automatic Cab Signal System (ACS) (US)

A system that automatically operates a display of signal aspects in the cab of a train as well as the cab warning whistle.UoS

Automatic Code Insertion

The means by which, when a train terminates, the next working of its stock is automatically picked up by the signalling in IECC areas.RT

Automatic Coupler

An automatic coupler allows two vehicles to be attached to each other merely by pushing the two vehicles together.  There are various types and systems in use, which range from a simple automatic mechanical coupler (like the 'buckeye coupler' of US origin) to one which is remotely controlled and can connect and secure air and electrical connections in one operation.  In Europe only used for Multiple Unit trains and specialised types of rolling stock.  The proposed UIC autocoupler was shelved in the 1970s due to cost but Germany and France are currently carrying out trials of a traction only autocoupler.UoS

Automatic Dropping Device

Mechanism which causes a damaged or displaced pantograph to drop automatically to limit (further) damage to the overhead line equipment.RT

Automatic Fare Collection (AFC)

A revenue collection system common on metros and urban railways which requires the passenger to buy a ticket and use it to release an entrance and / or exit gate to permit access to or exit from the railway.  AFC reduces the need for ticket checking staff and reduces fraud by passengers and staff. UoS

Automatic Level Crossing

Includes AHB, ABCL, AOCL and AOCR level crossings plus those protected by miniature red/green warning lights.  RT

Automatic Open Crossing (remotely monitored)

Now only one left on the Network Rail system (in Scotland.)RT

Automatic Railway Inquiry Systems

In Europe a prototype system to provide passenger timetable information.RT

Automatic Route Setting (System) (ARS)

Electronic or relay based system which sets routes using information from a train describer and the timetable without the need for intervention by a signaller.UoS

Automatic Signal

A colour light signal which operates automatically as trains travel onto and off track circuits ahead.RT

Automatic Stop Arm (US)

See Automatic Train Stop (UK).UoS

Automatic Systems

The hierarchy of the components of automatic assistance to the operation of trains is not clearcut.  Different authors advocate different structures. The structure presented in the figure below is based on PhD work by D.Woodland.

Automatic Train Control (ATC)

The system for automatically controlling train movements and directing train operations.  ATC requires automatic train operation (ATO) and automatic train protection (ATP) subsystems and has features which enhance operational safety, e.g., through the separation of trains by implementing a conflict free timetable, train detection and interlocking of routes.  ATC allows the automatic control of trains throughout a railway network, obviating the need for train drivers.  The Docklands Light Railway in London provides a good example of this type of operation. (Australians use this acronym to describe automatic train protection.)UoS

Automatic Train Monitoring (ATM)

Subsystem to monitor the train service by means of train describers, track circuit occupation or balise based data collection.  ATM is normally a subsystem of automatic train supervision (ATS) and is sometimes also referred to as train service monitoring.UoS

Automatic Train Operation (ATO)

The subsystem within the automatic train control (ATC) system which performs functions otherwise assigned to the train operator (driver).  ATO is not generally considered to be safety critical since interlockings and automatic train protection (ATP) ensure that trains’ routes and movements cannot conflict. Driverless operation of trains requires the transmission of control data using track circuits, inductive loops, balises or radio signals.  Radio signals can be diffused by broadcast or leaky cable feeders.UoS

Automatic Train Protection (ATP)

The subsystem within the overall train control system which automatically ensures compliance with or observation of some or all speed restrictions or movement authorities’.  Normally, the term ATP refers to the provision of failsafe protection against collisions, excessive speed, and other hazardous conditions which may arise during train movements by preventing trains from ignoring control commands.  This definition covers what could be described as ‘Comprehensive ATP’ (see below).  Less effective systems (such as TPWS, AWS and Trainstops) are sometimes also classified as ATP.  As a result, the following hierarchy of functionality is proposed, with ATP as the ‘global’ term: Warning Systems ‘systems assisting observation of movement authorities, based upon manual activation’, e.g., the Driver Reminder Appliance (DRA); Automatic Warning Systems ‘systems automatically assisting observation of movement authorities’, e.g.  the standard British AWS system; Automatic Train Stop ‘a system automatically enforcing compliance with the limits of movement authorities’; Partial ATP ‘a system automatically enforcing compliance with speed restrictions and movement authorities at some locations or for some vehicles’; Comprehensive ATP ‘a system automatically enforcing compliance with all speed restrictions and movement authorities (for all vehicles) within a given area’.  This type of system is often divided into two subcategories, Intermittent ATP and Continuous ATP. There are many different types of implementation but all require the transmission of control data using track circuits, inductive loops, balises or radio signals.  Radio signals can be diffused by broadcast or leaky cable feeders.UoS

Automatic Train Regulation (ATR)

Subsystem to ensure that the train service returns to timetabled operation or to regular, fixed headways, following disruption. ATR subsystems adjust the performance of individual trains to maintain schedules.  ATR is normally a subsystem of automatic train supervision (ATS).UoS

Automatic Train Reporting

Electronic system for reporting train movements based on the passing of train identities using a signal panel train describer.RT+UoS

Automatic Train Stop

A wayside system that works in conjunction with equipment installed on the vehicle to apply the brakes at designated speed restrictions, block signals or on a dispatcher’s signal, should the driver not respond.  Once actuated, the brakes are applied until the train has been brought to stop.  See Train Stop.UoS

Automatic Train Supervision (ATS)

The toplevel system in real time train control which regulates performance levels, monitors the trains in service and which provides data to controllers to adjust the service to minimise the inconvenience otherwise caused by irregularities.  The ATS subsystem also typically includes automatic train regulation functions which are implemented through an automatic routing system (ARS).  ATS requires automatic train monitoring (ATM) and service monitoring to be able to adjust the timings of trains appropriately.  ATS supports automatic train control by managing the routes or network.UoS

Automatic Vehicle Identification

Semiautomatic mechanism for reporting of train movements based on the location of freight rolling stock and subsequent translation to actual train identities/activities reported to TOPS (generally limited to electricity coal services).RT

Automatic Vehicle Identification (AVI)

Transponder based system to identify the number and other useful information of any vehicle in a train using a trackside interrogating unit.  The passive UIC standard system is lowcost (about US$40 per unit for the hardware).  AVI components are also being used for lowcost ATP applications. UoS

Automatic Warning System

Used to give advance warning to drivers of a signal aspect, a temporary speed restriction or a permanent speed restriction at least 30% slower than the previous limit.RT

Automatic Warning System (AWS)

British system for alerting the driver to a signal aspect which requires action (horn for danger) or indicating a clear signal ahead (bell for green).  Based on a trackmounted permanent magnet with an electromagnet to cancel the warning.UoS

Autonomous Traction

A form of traction where the power source is contained wholly on the vehicle (Diesel, gas turbines, battery, flywheel, coal, wood) allowing the vehicle to travel a design range between refuelling. UoS

Auxiliary Wayside System

A backup or secondary train control system, capable of providing full or partial automatic train protection for trains not equipped with train borne CBTC equipment, and/or trains with partially or totally inoperative train borne CBTC equipment.  The auxiliary wayside system generally includes train borne equipment and may also provide broken rail detection.UoS

Auxiliary Wire

See Compound Catenary.UoS


The ratio between the time during which a piece of equipment (or a human being) is available for operation (whether or not being used) and the total period during which it is needed.  Scheduled maintenance, for example, reduces the availability of rolling stock unless carried out during nonservice hours.UoS


The part of a wheelset which links the two wheels.  Normally, wheels are pressed onto shoulders machined onto the axle.  Axles normally have outside bearings which sit in axleboxes.  Inside bearings are more difficult to install and maintain but reduce the unsprung mass acting on the track.UoS

Axle Arrangement

The way in which powered and nonpowered axles are arranged under a vehicle.  The most commonly used description distinguishes between powered and nonpowered axles where the letter "A" stands for a single powered axle, "B" for two, etc.  while numbers stand for the nonpowered axles:

  • A1AA1A is the axle arrangement of a locomotive with two bogies, each of which has two powered axles with an nonpowered axle in between;
  • C0C0 or CoCo is the axle arrangement of a locomotive with two bogies with three powered axles.
Other wellknown arrangements are B0B0B0 (BoBoBo) for heavy locomotives and 1AA1 for EMU cars.UoS

Axle Counter

Track mounted equipment which counts the number of axles entering and leaving a track section at each extremity; a calculation is performed to determine whether the track is occupied or clear.RT


Back Drive

Mechanical arrangement to provide an actuation force away from the tip of a set of points, used to ensure that the switchblades are correctly positioned throughout their length.UoS

Balancing Segment

An accounting function defined so that the general ledger will not allow unbalanced journal entries to be posted.  For example, if your business unit segment is a balancing segment, general ledger ensures that, within every journal entry, the total debits to unit 01 equal the total credits to unit 01.  RT


Track mounted device for communicating with passing trains.  Most are mounted on a sleeper in the middle of the track (4 foot).  We distinguish inductive and radio based balises, active and passive balises and intelligent and dumb balises.  All balises transmit or transmit and receive information in the form of telegrams, e.g., one of the ERTMS standards allows the transmission of up to 512 bits of information three times while a train is passing at up to 250km/h.

  • inductive balises operate at low frequencies and use inductive coupling between a fixed coil (antenna) and a moving coil on board the vehicle;
  • radio based balises operate at several hundred MHz and use aerials embedded in the balise and suspended underneath the front end of the vehicle;
  • passive balises must be powered up by the passing train, usually using a 100kHz signal coupled inductively.  The balise detects the presence of a train and automatically transmits the stored data.  This is the most common type of balise;
  • active balises use an external supply to transmit data and are often used to power track loops (EUROLOOP) where data is transmitted continuously;
  • dumb balises simply transmit fixed information such as the balise number, number and position of the next balise(s), gradients and speed restrictions etc.;
  • intelligent balises transmit a combination of fixed and variable information such as the aspects of signals associated with the balise.  In some cases they can also receive and process information from the train.
It is possible to have most combinations of the types, e.g., active intelligent inductive balises.UoS


Selected material placed on the sub grade (US: roadbed) to support and hold the track with respect to its alignment within the bounds of specified top (vertical) and line (horizontal).  Ballast preferably consists of accurately graded hard particles, normally stone, easily handled in tamping, which distribute the load, provide elasticity, drain well and resist plant growth.  Generally, ballast must consist of broken stones.  Granite is a very suitable material thanks to its toughness.UoS


The graded stone used for drainage and support of the track.  The advantage over slabtrack is that it is easy to move for maintenance work.RT

Ballast Cleaning

The process of separating dirt (fines and crushed ballast) from the ballast by shaking followed by grading of the stone and by depositing the stone which is still usable back onto the track.UoS

Ballast Cleaning

The removal of existing ballast using a machine which grades the excavated ballast, returns good stone to the track and takes fine stone and spoil for disposal.RT

Ballast Mat

A 50 to 70mm thick elastomer mat placed under the normal track ballast on top of a rigid slab or on top of the sub grade to absorb vibration and to assist drainage.  Normally, the ballast mat is placed on an intermediate layer of sand.UoS

Ballast Section

The cross section of a track around and under the sleepers (crossties) and between and above the toes of the ballast slopes.  This section may include subballast.UoS

Ballast Shoulder

The portion of ballast between the end of the sleeper (tie) and the toe of the ballast slope.  It distributes the traffic load over a greater width of sub grade and helps hold the track in lateral alignment.UoS

Ballast Tamper

A power operated machine for compacting ballast under sleepers (crossties) using strong tynes which are pushed into the ballast on either side of the sleeper.UoS

Ballast Tamping

Compacting ballast under the sleepers to maintain the line and top (US: surface) of track.UoS

Banner Repeater

A signal whose function is to repeat the indication shown by another signal when the driver cannot see the latter.RT

Barrow Crossing

A level crossing at the end of a station platform for use by (or under the supervision of) rail staff only.RT

Base Station Controller (BSC)

Electronic unit controlling the transmissions from several radio antennas in a radio block system.UoS


A metal casting which supports and holds a flat bottom rail on a sleeper.RT


(1) Deformation of the surface of the railhead due to wheel impact (P1 and P2 forces), usually close to the joints (ends of rails) or (2) Receding (sloped) wall as encountered in cuttings and on ledges.UoS

Bay Line

A dead end line adjacent to a platform.RT


Timber (or concrete) transverse sleeper supporting the rails in switch and crossings. RT

Bearing Platform

The top surface of an abutment or pier upon which the superstructure span is placed and supported.  For an abutment it is the surface forming the support for the superstructure and from which the hackwall (US) rises. For a pier it is the entire top surface.  (US: Bridge Seat.)UoS

Bell Crank

L-shaped casting or fabrication pivoted in the centre to change the direction of an actuation force (usually used in switch drives, e.g., to create a backdrive.)UoS


Name occasionally used for a track circuit.RT

Berth Offset

The difference between the time a train actually occupies a track circuit and the time recorded in TRUST for the event.RT

BiDirectional Lines

Rail Lines which are fully signalled to take trains in both directions.RT

BiDirectional Signalling

Allows trains to run in either direction over the same section of track under the control of an interlocking (builtin safety system) which prevents collisions.  Bidirectional signalling is very useful in releasing for maintenance a single track of a twotrack railway but it is more complex and expensive to install than single direction signalling.  Singletrack lines always have bidirectional signalling.  (Swiss Term: banalised track.)UoS


A layer under the ballast to stop clay and soil seeping through.RT

Blast Cleaning

The preparation of a surface by impingement of a stream of abrasive of high kinetic energy particles ("shot").  RT+UoS

Block (Section)

A length of track of defined limits onto which one train only is usually allowed at any one time (exceptions include the joining of trains, split platforms and breakdown recovery).  The access to and use of the block section is governed by verbal instruction, track warrant, token or track circuit controlled block (section) signals or by some other type of signalling.  Older type block signalling requires the presence of block instruments to communicate with adjoining signal boxes.UoS

Block Bells

These provide a unique manual system of communication between signal boxes.  Using an electric single stroke tapper, messages can be passed between boxes in the form of bell codes.RT

Block Controls

Enhancements to the basic block instruments used in an Absolute Block area. RT

Block Indicator

Electrical system which allows communication between two adjacent block posts and which indicates the state of the line between the signal boxes.  The system uses a simple twowire link and relies on bellcodes in Britain and polarities in the link between the posts elsewhere.UoS

Block Instrument (see Block Indicator)

Block Section The section of line between the section signal of one signal box and the Home signal of the next signal box ahead.RT

Block Signal

A fixed signal at the entrance to a block section, to govern trains and light running locomotives entering and using the block.UoS

Block Station

A place at which block signals are located and from where they may be operated.UoS

Block System

Maintains an interval of space between trains (see also Absolute Block).RT

Block System, Automatic

A series of consecutive blocks governed by automatic block signals actuated by a train or engine or by certain conditions affecting the use of the block.UoS

Blyth & Tyne

The freightonly route to the east of the ECML between Newcastle and Morpeth, originally built by the Blyth & Tyne Railway Company.RT


Slang for a signal.RT


Traditional slang for a signalman (The original signalmen were actually Railway Police Officers.)RT

Bogie (UK)

A four or sixwheeled frame, normally used in pairs under longbodied railway vehicles and on locomotives or individually inbetween two sections of an articulated vehicle.  The bogie has a central pivot point, which allows it to turn as the track curves and it thus guides the vehicle into the curve.  The pivot point can be real or it can be created by links and flexibility in the suspension.  There are almost as many bogie designs as there are bogies.  Allwelded boxframe bogies with some steering capability are currently the fashion in Europe.  Good design is crucial to achieve a good ride quality, although track condition is also very important in assuring this.  See also Articulation.  (US: Truck.)UoS

Bolted Rail Crossing

A rail crossing or "frog" assembled from mill rolled and machined rail of bolted construction, as distinguished from solid cast crossing frogs.UoS


Cable or braid used to create the same electrical potential in two places, e.g.  to link a signal mast to the rail (earthbond) or a part of the electrification system to another part.  Red bonds are used on 25kV electrifycation.  (See also Impedance Bond.)UoS


A financial transaction where the contractor deposits a defined sum of money with a third party (usually a bank) that is held in bond until the defined tasks have been satisfactorily completed.RT


The technique or action of creating the same electrical potential in two different places.UoS


A Concrete Panel Which Forms Part Of The Road Surface Over The Track At A Level Crossing. RT

Boxing (US)

See Hunting (UK).UoS

Brace, Rail

A device used points (switches or turnouts), movable crossings (frogs) etc., in combination with point bearer plates, for ensuring the correct distance between rails.  Also used on rails in sharp curves to maintain the gauge & prevent overturning of the rail.UoS

Braking Distance

The distance a train needs in which to stop (or to reduce speed) from travelling at a given speed.RT

Branch (Line)

Track carrying trains from the mainline to destinations on lower priority routes than the mainline.UoS

Bridge Assessment File

The file containing or referring to all relevant records resulting from the assessments carried out on a bridge.RT

Bridge, Ballast Deck

A bridge with a solid floor provided with drains and covered with ballast, to provide normal and uniform support for track which conforms generally to the standard construction used for the tracks where they are constructed on sub grade (roadbed).  Requires more height than a bridge with slabtrack or where the sleepers rest directly on the structure.UoS

Bridge Bash

(see Bridge Strike).UoS

Bridge, Ibeam

A stringer type bridge in which the stringers are steel Ibeams that directly support the track or ballast section.UoS

Bridge Strike

A generic term to describe an incident where a road vehicle has hit the overhead structure of a rail bridge.  This is a common reason for train delays as the line often cannot be reopened until the bridge is inspected by a suitablyqualified railway employee.RT

Bridge Strike Nominee

A person who has been certified as competent to implement the procedures for reopening lines at 5 mph, as contained in the Rule Book Appendix ‘Bridges Struck by Road Vehicles’.RT

Bridge, Through Span

A bridge in which the track is carried between girders or trusses.  Girder and pony truss (US) bridges (trusses without overhead braces) are called halfthrough spans; truss bridges with overhead bracing are called through spans.UoS

Bridge Tie (US)

A sawed sleeper or tie usually preframed and of the size and length required for track on a bridge, directly resting on the structure of the bridge.  Usually made from hardwood.UoS


Name of the company which runs a mailing system using the DX (document exchange) network. RT

British Rail Incident Monitoring System

Computer database which provides statistical information on accidents and safetyrelated incidents.RT

British Rail International

The former arm of BR responsible for running overseas offices and selling tickets to continental destinations.  Now trading under SNCF ownership as Rail Europe.RT

British Rail Staff Association

A national association for the benefit of all membersRT

British Standard

A standard published by the British Standards Institution.  Its alphanumeric identity is prefixed by BS.  Most British Standards are being superseded by ISO standards.  RT+UoS

Broad Gauge

Line a track wider than the standard gauge of 4 ft 8½ in (1435mm).UoS


A company which built a type of vehicle capable of running on both road and rail; normally used to travel by road to aid a derailed rail vehicle or to travel to the nearest road access for a remote work site.RT


Failure of a rail by an inelastic change in alignment (usually as a result of compression due to elevated temperature).  To lose line of track by bulging.UoS

Bull Head Rail

An obsolete UK rail profile still in wide use whose top and bottom profiles are mirror images of each other.  The rail is symmetrical with respect to the web centreline and is theoretically reversible to extend its life. The designer’s intention was that one could transpose the rails between right and left and then turn them upside down for a further two uses.  Corrosion and stresses in the effective foot make this reversal impossible.  See also Rail and Flat Bottom Rail.UoS+RT

Bump Stop

Hard rubber suspension component which stops a movement close to the end of the spring travel of a lateral or vertical suspension.UoS

Business Management Information System

A suite of custom and offtheshelf software being developed to manage Railtrack finance, procurement and project management, formerly known as FBMIS or FBIS.RT

Business Risk Assessment

An assessment of the (nonsafety) business risks implicit in a change proposal and associated investment plans.RT

Business Route Selection

commerciallybased unit of route measurement which enables costs and income to be measured for defined sections of route, based on volume and type of customer usage.RT

Butt Weld

A weld joining two abutting surfaces by depositing weld metal within an intervening space or by melting both rail ends and then pushing them together.  This weld serves to unite the abutting surfaces of the elements of a member or to join members by their elements abutting upon or against each other.  Butt rail welding of one rail to another can be accomplished inplant or on site by electric resistance fusion (Flash Butt Welding) or by an aluminothermic process in the field.  UoS


C Change

A major business initiative launched in June 1996 to rationalise, clarify and standardise Railtrack processes and procedures.  The primary focus was to make significant improvements in customer service and control of key activities. RT


The space in the power unit or driving unit of the train containing the operating controls and providing shelter and seats for the driver or engine crew.

Cab Signal

A signal installed in the driving cab of the train repeating or in lieu of lineside signals.RT

Cadbury Code

Defines the accountabilities of the board, chairman, and nonexecutive directors of a company, in respect of corporate governance, internal control and financial reporting.RT


The term used to denote the raising of the outer rail with respect to the inner rail on curved track to allow higher speeds than if the two rails were level.  Cant assists in creating the force necessary to accelerate the train laterally to traverse a curve.  If a track was canted to the level required to generate the full curving force (equilibrium cant) for the maximum speed of the fastest train, a slower train could topple over.  A compromise value of cant is therefore used, leading to ‘cant deficiency’ at higher speeds.  Cant is what stops your coffee spilling when you go round a curve (US and Continent: SuperElevation).UoS+RT

Cant Deficiency

The theoretical amount by which the outer rail would need to be raised to reinstate equilibrium for a train travelling through a curve faster than the equilibrium speed.  The existence of cant deficiency will result in pushing your coffee to the outside of your cup.RT+UoS

Cant Excess

For a train travelling slower than the equilibrium speed on a curve, the theoretical dimension by which the outer rail would need to be lowered to reinstate equilibrium.RT

Cant Rail

The part of a vehicle or traction unit at which the profile between the bodyside and roof changes.RT


A type of overhead line support, consisting of a mast to one side of the track with supports for contact wire and catenary wire.RT+UoS


Capital expenditure (see also OPEX). Funds spent on fixed assets (e.g., the Heathrow Express infrastructure) which are not charged against company profit.RT

Capital Project

A project resulting in the production of a physical asset for a company.RT

Car (UK)

Only exists in combination, e.g., railcar.  (US: any nonpowered rail vehicle). Car, Hand a four wheeled, hand operated works vehicle for transporting staff and tools.  (UK: Trolley)UoS

Car, Motor

A motordriven works or inspection vehicle.  (UK: Powered Trolley).UoS

Carriage (UK)

Passenger carrying rail vehicle, also referred to as Coaching Stock.  (US: Coach)UoS

Carriage Line

A line used to move empty rolling stock / carriages only.RT

Carrier Drain

An impervious drain designed to carry water from place to place instead of collecting water from the surface or surrounding soil directly.RT

Catastrophic Risks

Events with a potential for multiple casualties.RT

Catch Point

Point leading to a very short dead end or simply used to derail rolling stock attempting an unauthorised movement.UoS

Catch Points

A pair of sprung trailing points usually located in gradients steeper than 1 in 260.  Their purpose is to derail any train running back without authority or out of control.  These were a requirement before all vehicles had automatic brakes.  Now they are being progressively removed. Sometimes they are worked from a signal box rather than being spring operated.RT


(1) The catenary wire or cable (also known as the messenger wire) carries the contact wire by means of dropper wires.  The term was chosen because the catenary wire assumes more or less the shape of the curve adopted by a suspended chain or wire.  (2) Generic term used for a power supply arrangement incorporating at least a contact wire and a catenary wire connected by droppers.  See Overhead Line.UoS

Catenary System

Generalised term used to describe the whole overhead line equipmentUoS.

Cat’s Eyes

Slang term for a position light shunting or subsidiary signal.RT

Cattle Guard (grid)

A rail high panel of material difficult for hoofed animals to traverse, used to continue a stock fence across a railway line.  See Stock Guard.UoS

Central Door Locking

A secondary locking system retrofitted to certain slam door trains and controlled by the guard which prevents passengers from opening the doors while the train is moving.RT

Centralised Traffic Control (CTC)

Remotely controlled system of signals and points under which train movements are authorised by station and block signals whose indications determine the precedence of trains.  The manipulation of automatic and/or cab signals and poweroperated turnouts is effected from a central location where indications on panels or displays indicate the position of trains and the state of signals and points.  (UK: Power Box or Integrated Electronic Control Centre IECC)UoS

Centre Siding

A length of track laid between two running lines for the purpose of reversing trains, usually beyond a station.  It allows a train to reverse direction without crossing a track carrying through trains.  Sometimes referred to as a "reversing siding".  (US: pocket track or turnback track). UoS

Certificate of Acceptance

A certificate that is issued in accordance with GO/RT/3270 Route Acceptance, which requires a Certificate of Conformance to be issued for the locomotive design, construction, testing, examination and maintenance.RT

Certificate of Authority to Operate

A formal certificate signed and issued by the RSAB documenting the conditions under which a T&RS Route Acceptance Request has been accepted.  This certificate specifies the equipment, the equipment configuration, operational requirements and limitations, route constraints and network factors within which approval has been granted for network operations.RT

Certificate of Technical Acceptance

The formal signed certificate issued by the RSAB confirming that a technical design proposal conforms to Network Rail technical standards for route acceptance and represents a suitable basis for development for network applications.  This certificate specifies the equipment, the equipment configuration, limitations, route constraints and network factors within which approval has been granted.RT

Cess (UK)

The area either side of the railway immediately off the ballast shoulder.  This usually provides a safe area for authorised workers to stand when trains approach.RT+ UoS

Chain (UK)

Unit of length common on UK railways (80 chains to a mile, 22 yards per chain and 1 chain = 66 feet.)RT+ UoS


The cast steel fixture on a sleeper, which secures rail (particularly bullhead rail) in the correct position.  Depending on the design, of which there are many, the rail is secured to the chair by a form of clip, key or spike.  UoS

Chargehand (or Chargeman)

An obsolete job title for a train operator or infrastructure owner employee who has a supervisory role on a station platform.RT

Check Rail

(1) A rail laid parallel to and inside a running rail to prevent wheels from being derailed or to hold wheels in their proper alignment while crossing the stock rail.  Check rails prevent wheels from striking the blades of points and the tips of crossings. 
(2) An additional pair of rails laid parallel to and between the running rails on bridges, bridge approaches, and in other critical locations, to keep derailed wheels on the sleepers and near the running rails.  (US: Guard Rail.)UoS

Check Rail Clamp

A device consisting of a yoke and fastening devices fixing the relative positions of the running rail and guard rail.  Not all checkrails have clamps.UoS

Chisel, track

A handheld tool to be struck by a sledge hammer, for cutting rail by scoring the base and web until breakage occurs, or for similar cutting.  A rail cutter.UoS

Circuit, Track

See Track CircuitUoS

Claims Allocation and Handling Agreement

An agreement between railway operators which empowers Railway Claims Ltd to act on behalf of the industry and its contractors for an accident or incident where a third party claim affects a number of organisations.RT


A device used to secure the closed switch of a pair of points to the stock rail.  Sometimes known as a clip.RT

Clamp Lock, or Clamplock

A point operating mechanism which locks the points by directly clamping the closed switch rail to the stock rail.  Normally operated hydraulically.RT+UoS

Clamp Lock Heater

A cartridge type heater fitted to a clamp lock mechanism operating the points blades.RT

Class of Train

Class 0 Light locomotive (locomotive running on its own; Class 1 Express passenger trains, mail trains and some emergency trains; Class 2 Stopping passenger trains; Class 3 Express parcel trains; Class 4 Express freight trains 75mph maximum speed; Class 5 Empty coaching stock trains (passenger vehicles running empty); Class 6 Express freight trains 60mph maximum speed; Class 7 Freight trains with 45mph maximum speed; Class 8 Freight trains with 35mph maximum speed; Class 9 Eurostar trains.  RT + UoS

Clearing House Accounts Payable

A system for financial settlements between Network Rail and between TOCs.RT


Often called a "clamp", that is used to secure the closed switch of a pair of points to the stock rail, to prevent unauthorised or unintentional movement of the points.RT

Clip, Switch

The device by which the switch rod is joined to the switch rail.  It is usually united with the switch rail by bolts or rivets.  It sometimes has staggered bolt holes or similar devices in the horizontal leg for making detailed adjustments in the positions of the switch rails.UoS

Clip, Transit (switch)

A switch rod clip drilled with several holes in a line diagonal to the axis of the switch rod, for effecting adjustments in the throw of the switch.UoS

Clockface Timetable

A timetable where trains run at regular intervals (e.g., every 10 minutes.)RT

Closed Circuit Television

Often used for station security and monitoring level crossings.RT

Closure Rail (US)

The lead rails connecting the heels of a switch with the toe ends of a frog. UoS


A type of railway carriage, usually with a centre aisle and two rows of seats.UoS


Allowing a train to freewheel (on the flat or downhill) to minimise energy use.  Of the 50 non stop electrified miles between London and Brighton, 29 miles can be run with the train coasting.  UoS

Coasting Allowance

Additional time in a schedule to allow trains to coast part of the journey.UoS

Code of Practice

A statement of best practice whose use is not made mandatory by the issuing authority.RT

Collector Drain

See surface water drain.RT

Communications Based Train Control (CBTC)

A continuous automatic train control system characterised by: (i) high resolution train location measurement, independent of track circuits; (ii) continuous, high capacity, bidirectional traintotrack RF data communications; and (iii) trainborne and wayside vital processors capable of implementing vital functions. In the UK it is known as Transmission Based Signalling (TBS).  In Europe it is ETRMS Level 3.  UoS

Communications Engineer

An engineer, acting for or on behalf of Network Rail, who is competent in railway communications and who is appointed in accordance with section 2 of RT/E/P/30022.RT

Compound Catenary

An overhead line arrangement which includes a catenary wire, auxiliary wire and contact wirelinked by droppers.  All three wires share the traction element (UK MK 1OLE).UoS

Compromise Bars (US)

Specially machined rails to connect rails of different section in such a way that the gauge sides and the top of the head and running surfaces are held in line.  Also called offset bars.UoS

Condition of Track

This is a reason for a restriction below normal speed which ensures that trains pass at a safe speed over a track or a bridge or an embankment which is not currently fit for line speed.RT

Conductor Rail

An additional rail (or rails) provided on those electric railways where power is transmitted to trains from the track.  Often referred to as the 'third rail' or 'current rail', it is normally at positive potential and is mounted on insulators to the outside of and slightly higher than the running rails.  The return of the circuit is via the running rails.  The current is collected by the train through 'shoes', attached to the bogies, which slide on top, along or under the rail.  The continuity of conductor rails must be broken at junctions in the track to allow continuity of the running rails. Such 'gaps' may cause momentary loss of power to the train.  There are cases from time to time of trains becoming 'gapped' at complex junctions, i.e.  they stall over a gap and have to be rescued by another train.  London Underground has a fourth rail (negative) for a completely insulated circuit.  This is known as a fourrail system and the running rails are at an offset potential between the contact rails.  Modern 3rd rail systems are under – pinning to allow the installation of protective (insulating) covers.UoS

Confederation of British Industry

Network Rail is a corporate member, therefore any designated manager is eligible to attend members’ meetings.RT


The taper profiled onto the surface of a railway wheel that assists guidance around curves.  Usually 1:20 or 1:20 with part at 1:40.UoS


Train formation, e.g., 'This vehicle was in the ’consist'.  The sum of all vehicles in a train (for all train types).  UoS

Construction Work

Maintenance, renewal, new work and commissioning in relation to the following:

  • civil engineering, signalling, electrification, telecommunications, plant and electrical distribution and related computer systems;
  • demolition and dismantling operations;
  • waste removal resulting from demolition or dismantling.RT

Contact Patch

The contact area between the wheel and the rail.  Normally said to be about 1cm2 in size and experiencing very high pressures.  See also rolling contact fatigue.UoS

Contact (Trolley) Wire

The overhead wire, sometimes referred to as trolley wire, which the pantograph of an electric locomotive, rides against (contacts) to collect its electrical current (source of power) and which is carried by the catenary or messenger wire.UoS

Contact Wire

Harddrawn copper, silver or (in Russia) aluminium wire, which is normally suspended from a catenary wire by droppers and is swept by the stainless steel contact strip (Japan) or aluminium contact piece (France DC electrified lines) of the pantograph.UoS

Contact Wire

The overhead wire touched by an electric train’s pantograph in order to draw power.RT


Special type of overhead wire used where clearances are tight.  The term is a contraction of ‘contact’ wire and ‘catenary’. RT

Continuous Welded Rail

Comprises rails welded together to form a single rail length over 36m (120ft), or 55m (180ft) in tunnels with a limited temperature range.RT

Continuously Welded Rail

A number of lengths of rail welded together to stretches of 300m or longer in a factory or permanent way yard and then welded together in a seamless manner.  Expansion joints are fitted to prevent buckling.UoS

Contract Approval Group

A committee, chaired by the Head of Procurement, that reviews and approves proposed contract strategies, and contract awards over £5m.RT

Contract Check

An activity which assesses the extent to which a contractor’s work, procedures or systems meet his contractual obligations.  This includes systems, technical and safety checks, and inspections of the contractor’s activitiesRT

Contract Check Plan

A plan indicating activities, timescales and Network Rail sections responsible for undertaking individual verification of elements of all maintenance contract work coordinated and managed by the Senior Contracts Manager.RT

Contract Instruction

An instruction by the Employer to the Contractor relating to an activity which is included in the terms of the contract and which does not vary the contract.RT

Contract Strategy

The precise way in which an individual contract is organised, planned, and implemented.  It will include a timetable for preparation, invitation to tender, and award of contract, with the necessary approval stages involved.  It will also include key criteria for the conditions of contract, the approach to the market, the way in which available competition will be exploited, and the tender evaluation criteria.RT

Contract Strategy Report

A report prepared by the Procurement Manager in advance of an invitation to tender to define the strategic approach when entering the supply market and the proposed structure of the intended contract.RT


A generic term used to describe a company, consultant, partnership or individual supplying works, goods or services to Network Rail.RT

Contractor Check Plan

The infrastructure maintenance contractor’s plan for internal checking of their end productRT

Contractor’s Assurance Case

A document specific to a particular maintenance or renewals contract in which a contractor sets out to demonstrate his intention, competence, capability, organisation, risk assessment, and safety management system to undertake the contract work or service requirements in a safe manner, formerly known as Contractors Railway Safety Case.RT+UoS

Contractor’s Core Safety Case

A set of documents specified by and provided by the contractor to demonstrate that he has the resources, skill, experience and ability to safely carry out all tasks in pursuance of his undertaking.  These documents are neither project nor contract specific.RT

Contractor’s Core Safety Case Review Panel

A panel of no more than four members set up by the Director Line Safety and composed of representatives from both the process and technical functions.  Members may be chosen from Zone, Property, Project Delivery and Engineering and Production management units, as well as professional heads, engineers and specialists for resourcing the panel.RT

Control Centre of the Future

Computerised enhancements to the facilities available in control rooms, an AEA Technology Rail project.RT

Control Duty Manager

The person in charge of the shift in Network Rail zone control.RT

Controllable Income and Expenditure

Income and expenditure able to be regulated/controlled by the cost centre budget holder.RT

Controlled Copy

Copy of an important document whose recipients receive updates whenever the document changes.UoS

Controlled Document

A document specifying key safety, environmental, procedural or technical aspects of the work of Network Rail staff which must be made available to post holders on a controlled basis in order to allow them to carry out their duties.RT

Conventional Interoperability Directive

A European Union Directive which requires that national railways technical and operational standards are gradually unified.UoS

Corrugated Rail

Railhead with regularly spaced ridges and valleys at 900 to the direction of travel which can have a variety of causes, not yet fully explained. UoS

Cost Centre

A unique identifier in the set of accounts used to collect the costs relating to the specific activities of a manager within the budget approved.RT

Crane, track (also called maintenance crane)

A poweroperated crane used principally for positioning rails during track renewal, but having many similar uses in maintenance work.UoS

Creep Force

The force generated due to creepage.UoS


The ratio of the tangential velocity of the wheel, to the actual velocity of the train.UoS


(1) The ballast or the open space between two adjacent crossties.
(2) A crisscross structure of logs, timber, concrete or other members, used to retain a fill or as a bridge support.UoS

Cripple Line

Siding for failed trains.RT

Cripple Siding

Track used for storing failed rolling stock.UoS

Crippled Rail

A rail that has been locally bent by mishandling, derailment or other impact.RT

Criterion Based Interviewing

A technique used by suitably trained persons to select staff for appointment and posts (often used in conjunction with psychometric tests.)RT

Critical End Product

An end product that, in consideration of importance ranking and loss contribution, is assigned a value which is above W.RT

Critical Rail Temperature

The rail temperature to which continuously welded rail may be allowed to heat up before measures to protect traffic must be taken.  The CRT will depend on the stressfree temperature of the rail and the quantity and degree of consolidation of the ballast.RT

Critical Speed

Speed at which hunting continues without dying away.  Above this speed hunting increases and derailment can occur.UoS

Cross Level

Difference in height of the railhead surfaces of the two rails in tangent (straight) track.UoS

Crossing (UK)

Location in a point (turnout) or diamond crossing where the wheel crosses the rail which is not leading in its direction of travel.  This can be cast, fabricated or made using a combination of technologies.  Requires a flange way for the wheel flange to pass through.  High speed and heavy haul railways use swing nose crossings (moving frogs).  (US: Frog)UoS

Crossing Protection

An arrangement of signs or electric signalling devices designed to prevent accidents at grade crossings.  May include short arm gates or full gates.UoS

Crossing, Grade (Xing)

A crossing or intersection of a railway line and a highway at the same level or grade.  (UK term is "level crossing").UoS

Cross Level

The distance one rail is above or below another.  This quality measurement should not be confused with superelevation or cant in curves.UoS


A track providing a connection between two parallel tracks using two turnouts (sets of points.  A scissors crossover provides two connections, one in each direction, with a crossing in the middle.  In the UK, trailing crossovers are preferred over facing crossovers since they are perceived to be safer.  A facing crossover allows a train to change to a parallel track without having to reverse.UoS


Connection between two tracks which allows trains to pass from one to the other.RT

CrossSpan Wire

A wire stretched across tracks holding the OLE in its desired position.RT

Cross Tie (US)

The transverse member of the track structure to which the rails are spiked or otherwise fastened to provide proper gauge and to cushion, distribute, and transmit the stresses of traffic through the ballast to the roadbed.  Also see Tie (US) or Sleeper (UK).UoS


Small bridge or pipe carrying a stream under a railway or road.RT

Curve, Compound

A curve composed of two or more simple curves which join on common tangent points or common transition curves and which lead in the same general direction, i.e., to left or right, but each with a different radius.UoS

Curve, Easement

See: Transition Curve. UoS

Curve, Reverse

A curve composed of two simple curves which join at a common tangent point or by a short tangent track or a reverse transition curve, and bear in opposite directions, i.e., to left and right or vice versa.  (US: DogLeg)UoS

Curve, Simple

A curve in the form of an arc of a circle usually described as to its degree of curvature.UoS

Curve, Vertical

A curve in the profile of a track to connect intersecting grade lines and to permit safe and smooth operation of trains over summits and across sags.UoS

Curved Lead

The rail from the heel of the point to the toe of the crossing.UoS

Cut (US)

Uncoupling part of a Train.  (UK) referred to the sections into which a train was broken when passing over a hump in a marshalling yard (now obsolete). UoS


Dabbing InEnthusiasts’ jargon for trespassing on the network to take photographs of trains.RT


Semiautomatic mechanism for reporting of train movements based on the location of multipleunit rolling stock and subsequent translation to actual train identities/activities based on the GEMINI vehicle control system.RT


A locomotive hauling another.  In addition, a nonrevenue (nonpassenger) train movement.  Deadheading is a US term for empty train or light engine running.  The movement of surplus personnel, usually drivers, without them performing their duties.UoS

Deadman Device

A pressure or activity actuated alertness device to detect inattention or disability of a train driver (operator).  UoS

Deenergised Apparently Dead

Electric apparatus, such as overhead wires, third rail, transformers, switches, motors, etc., is deenergised when disconnected from the normal power source, but such apparatus is deemed dangerous to life until it is known to be properly grounded.UoS

Degree of Curvature

A measure of the sharpness of a simple curve in which a 1deg.  Curve is taken as the central angle subtended by a chord or arc of 100 feet and for which the radius is taken as 5,730 feet.  Railways in the US use the chord definition highways the arc definition.UoS

Delegated Authority

The authority, usually expressed in financial terms, that an individual post in the organisation has to enter into the specific transaction to which the authority relates.RT

Delegated Budget Authority

The authority to commit expenditure within approved budgets in running the business.RT

Delegated Procurement Authority

The authority to act on behalf of the Head of Procurement to commit Network Rail contractually to third party suppliers of works, goods and services.RT


The management team engaged by the Sponsor to manage the day to day delivery of a project to a scope and purpose consistent with the business case provided by the Sponsor (see Sponsor).RT

Departmental Advice (Blue)

Used for publishing the Sandite programmes worked by TASC units (see TASC).RT


The charge reflected in the financial accounts for the use and replacement of fixed assets.RT+UoS

Depth, Ballast

The depth from the bottom of the sleeper or tie to the top of the subballast or sub grade.  The ballast between the ties (in the cribs) is a part of the ballast section but its depth is not a part of the specified ballast depth.UoS


A track safety device to guide nonauthorised train movements off the rails at a selected spot, as a means of protection against collisions or other accidents. Modern day equivalent for catchpoints in areas with slow moving traffic.  Usually linked to a point giving access to a main line or through track.UoS


Anytime the wheels of a rail vehicle are off the head of the rail and on the ground.  Caused by collisions, mechanical failure, gauge spreading or flange climb.UoS


Proof that points are correctly set (and usually locked) in the "Normal" or "Reverse" position. Correct detection must be obtained before the protecting signal can be cleared.RT


A small disc shaped warning device, designed to be placed on the railhead for protection and emergency purposes.  It explodes when a train passes over, thus alerting the driver.  Detonators are being phased out.  Correctly known as a fog signal.RT+UoS


The planned movements for a set of rolling stock (e.g., a train, a multiple unit) for a day or any other period and involving several journeys, generally with different service (train) numbers.UoS

Diamond Crossing

Arrangement of a line where one track crosses another, without connection, at an angle of less than 90º, at grade.  Named after the pattern formed by the rails.UoS

Diesel Multiple Unit (DMU)

See Multiple Unit UoS

Differential Global Positioning by Satellite (DGPS)

Navigation based on signals received from four or five satellites with a correction factor received from a fixed position reference transmitter via terrestrial FM.UoS

Direct Fixation Track

A system to attach rails directly to a solid, nonballasted surface.  (UK: Slab Track). UoS

Direct Rail Services

Originally, the freight operating organisation of British Nuclear Fuels.  Now a medium sized freight operating company, active in coal traffic and infrastructure maintenance supplies.RT+UoS

Direct Traffic Control(DTC)

System of traffic control with sections of track identified with clear boundaries, where permission to proceed is granted remotely by a dispatcher.  Ordinarily, only one train may occupy a DTC block at a time.  Similar to train warrant control (TWC) except that the section entry timings are fixed by timetable rather than granted case by case.  DTC may be used in conjunction with track signalling in APB, ABS, or over "dark territory". UoS

Disability Discrimination Act (DDA)

Legislation requiring providers of services that are made available to the general public take into account the needs of people with disabilities.  Part 3 of the Disability Discrimination Act (DDA) came into force on 1st October 2004 and requires every business, large or small, from the local shop to restaurants, health clubs, dentists and supermarkets, to become more userfriendly for Britain’s 10 million disabled people.  The law means that businesses will need to make reasonable changes, such as adapting premises, removing physical barriers or providing the service another way, so that disabled people can use the service.  Failure to act can result in legal action.  This legal requirement has been anticipated by the railway industry and has caused substantial cost increases. UoS


The splitting of plans and expenditure into different headings and activities.RT+UoS

Displaced Asset

An asset owned but no longer in use.RT

Distant Signal (AU, CH, D etc.)

Hixed signal which indicates the state of the main signal on the approach to a block signal, station entry or exit signal etc.  It will not convey information as to conditions affecting the use of the track between the distant signal and main signal.  Distant signals are necessary where a train driver can not react fast enough once he or she sees the main signal.  Often combined with the previous main signal.UoS

Distant Signal (UK)

Fixed signal outside of a block system, used to indicate the state of the main signal on the approach to a block signal, interlocking signal or switch point indicator.  It does not convey information as to conditions affecting the use of the track between the distant signal and block signal, interlocking signal or switch point indicator with which it is associated.  The distant signal does therefore not include a red or stop aspect.  When "on" it is a warning that the next aspect could be red.  Distant signals are necessary where a train driver cannot react fast enough once he or she sees the main signal.  It is identified by a "D" marker (UK).  UoS+ RT

Division Point (US)

One of a number of sections of a large railway, run as an independent entity to the extent of having its own fleet of locomotives, engines, repair shops, officials, and clerical and operating personnel.  Sometimes only refers to the management of part of the infrastructure.  (UK: Area)UoS

Document Control Point

A nominated location where the person in charge will receive controlled documents, allocate controlled copy numbers, register them, acknowledge receipt and pass them to each addressee.  The person in charge will also register outgoing documents, and ensure receipts are received from each addressee.RT

Dog Leg (US)

Railway parlance for a sharp reverse curve in the track.  The term's basis is the comparable crooked appearance of a dog's hind legs.  (UK: reverse curve)UoS


Slang term for a shunting signal in ex LNER terminology.  Sometimes also known as a "Dod" or "Tommy Dodd".  Rt

Dolly, Rail or Timber (US)

A device consisting of one or more wide rollers mounted in a frame, used as a platform and as a truck for moving rail, long heavy timbers, and other items.  (UK: Trolley)UoS

Double End Electrical Section

A section of conductor rail or overhead line fed from two points.UoS

Double Yellow Aspect

A preliminary cautionary signal in four aspect signalled teritory, informing the driver to expect the next running signal to be at single yellow.RT

DoubleEnder (US)

A locomotive able to run in either direction.  Most European locomotives are of this type , unlike US ones which often run in back to back pairs.UoS

Down Line

Rail line taking trains away from London or another major city (generally).  However, there are exceptions, for example, Up to Cleethorpes and Up to Hull from Seamer West.RT

Drill, Track

A machine designed to operate horizontally to drill holes through the webs of rails, especially for track bolts.  It may be a oneman ratchet drill or a geared drill machine with a frame, rail clamps, feed screw, highspeed steel bit and chuck.UoS

Driver’s Safety Device

Device on traction rolling stock that will stop the train if the driver becomes incapacitated.  Popularly known as the "Deadmans Pedal" or Deadman’s Handle".RT

Driving Van Trailer

An unpowered van fitted with a driving cab from which a locomotive at the other end of the train can be controlled, thus enabling pushpull working.RT


Stainless steel or galvanised steel wire supporting the contact wire from the < size="2">catenary wire < size="2">and linking the two electrically.  Fixed to the contact wire with clips.UoS

Dual Gate

Electronic means of monitoring two selected regions of the timebase of an ultrasonic flaw detector.RT

Dual Voltage Locomotive (Train)

Locomotive or multiple unit train designed to operate over lines having two different electric traction power supply systems.  Locomotives have been designed to operate with up to four different voltages covering both AC and DC systems.  Some trains can operate on lines with either overhead or third rail current collection, as in the case of Eurostar Trains and UK Class 92 Channel Tunnel locomotives and some North East Corridor trains in New York.  Eurostar trains can handle 750Vdc (England) 1500Vdc (Holland + France), 3000Vdc (Belgium) and 25kVac (Belgium and France).UoS


Slang term for a shunting signal, ex LMS terminology.RT

Dwell Time

The time a vehicle or train spends at a station or stop to allow passengers to board and alight, measured as the interval between time of stopping and starting.UoS

Dynamic Braking

A train braking system using the traction motors of the power vehicle(s) to act as generators with the energy dissipated in brake resistors (rheostatic braking) or supplied to other trains via the supply system (regenerative braking).UoS

Dynamic Track Stabiliser

A self propelled ontrack machine for consolidating track ballast by inducing high frequency vibration into the ballast through the rails and sleepers.  This treatment allows resumption of operations at line speed after a maintenance intervention (tamping etc.).RT+UoS


Early Rationalisation of Signalling Railtrack’s accelerated programme of closing small signal boxes and concentrating work at fewer, larger signal boxes.RT

Easement Curve

See Transition Curve.)UoS

Economical Facing Point Lock

A mechanism that enables the movement of points and the facing point lock plunger to be operated by the same lever.RT


A performance management information system with downloaded information from PHIS.RT


A material made substantially from natural or synthetic rubbers.RT

Electric Multiple Unit (EMU)

The generic term for an electrically powered suburban or train where a separate locomotive is not required because the traction drive and control system is contained under or in the roof space of various cars in the train (see also multiple unit. UoS

Electrical Control Room

Responsible for control of current in the overhead lines.  On the LNE zone, located at Hornsey and Doncaster, with Cathcart controlling Alnmouth Berwick.RT

Electrical Control Room Operator

The person in charge of a shift in the Electrical Control Room.RT


A term used to describe the installation of overhead wire or third (or 4th) rail power distribution facilities to enable operation of EMU trains or trains hauled by electric locomotives.UoS

Electrified Territory

That portion of the railway consisting of main tracks, secondary tracks, sidings, yards and industrial tracks equipped for electric train operation by overhead line system or by third rail and necessary substations, transmission and signal power lines located above or adjacent to the tracks.UoS

Electro Magnetic Interference

Interference in the signalling system caused by inductive coupling with traction motors, transformer stray fields, radio waves being generated by electronic equipment etc.UoS

Electromagnetic Compatibility

The ability of electronic devices to function satisfactorily in the presence of magnetic and electric fields.RT

Electronic Data Interchange

A computer network enabling suppliers and customers to pass orders, invoices, and payments electronically.RT

Electronic Train Recording

Computer equipment installed in signalboxes where automatic TRUST reporting is not operative, to allow the signalman to record train passing times. Now known as Simplified Direct Recording (SDR).RT

Electronic Train Register Book

Being installed in manual signalboxes to replace the old manual train register.  A PC based system.RT

Elevation (US)

Height of outer rail in a curve: See Superelevation.UoS

Emergency Restriction of Speed

A reduction of normal speed which has to be applied in an emergency.RT


The bonding of insulating material to a metallic fishplate core under workshop conditions prior to the manufacture of a joint.RT

End Post

Block of insulating material in the shape of the rail crosssection used to separate, electrically, rail ends from each other (also known as ‘biscuit’ in Scotland).UoS

End post

The piece of an insulating rail joint which separates the rail ends.UoS

Energised Live (Dangerous to Life)

Electric apparatus, such as overhead wires, third rail, transformers, switches, motors, etc., that is energised when connected to the normal power source.  All systems are considered to be energised until a qualified individual establishes that the circuit has been deenergised and has applied a secure link to earth.UoS

Engine Burn (US)

Destruction of railhead metal caused by spinning locomotive wheels.  Engine Burn Fracture is a rail break caused by an engine burn.UoS

Engineering Safety Management System

The management system that was employed by Railtrack EE&CS to ensure best current safety management practice.RT

English, Welsh and Scottish Railway Ltd

The company formed when the three heavy haul rail freight companies (Loadhaul, Mainline and Transrail) together with Rail Express Systems, were taken over by Wisconsin Central Railroad Company.RT+UoS


Surroundings in which an organisation operates including air, water, land, natural resources, flora, fauna, humans, and their interrelation.  Note: surroundings in this context extend from within an organisation to the whole system.RT

Environmental Impact

Any change to the environment, whether adverse or beneficial, wholly or partly resulting from an organisation’s activities, products or services.  RT

Environmental Impact Assessment

The ongoing identification of environmental factors to determine the past, current and potential impact (positive or negative) of an organisation’s activities on the environment.  This process includes the identification of the potential regulatory, legal and business exposure, as well as health and safety impacts and environmental risk assessment.RT

Environmental Management System

The part of the overall management system that includes organisational structure, planning activities, responsibilities, practices, procedures, processes and resources for developing, implementing, achieving, reviewing and maintaining the environmental policy.RT

Environmental Policy

A public statement of the intentions and principles of action of an organisation regarding its environmental aspects, giving rise to its objectives and targets.RT

Environmental Statement

A document setting out the results of an environmental impact assessment.  It consists of three parts:

  • main study findings;
  • technical appendices;
  • nontechnical summary.RT

Equilibrium Speed

The speed of a train travelling through a curve where the passeger experiences no lateral force, whether to the inside or outside of the curve, the speed at which there is neither cant deficiency nor cant excess. RT

Equivalent Fatalities

All fatalities and injuries expressed in terms of fatalities where 10 major injuries equals 1 fatality and 200 minor injuries equals 1 fatality.RT

Equivalent Million Gross Tons Per Annum

A measure of the damage effect on the track caused by different types of trains running at different speeds and with different axle loads.RT


(1) Emergency Restriction of Speed: a reduction of normal speed which has to be applied in an emergency or (2a) Efficiency by the Rationalisation of Signalboxes and (2b) Early Rationalisation of Signalling, Railtrack’s accelerated programme of closing small signal boxes and concentrating work at fewer, larger signal boxes.RT+UoS

ETH Index

The Electric Train Heating Index states the power which a headend power unit must supply to a railway carriage for "hotelpurposes", that is, heating and air conditioning etc.  Also, the capacity of the headend unit to supply this power.UoS


Computer network system.RT

Ethylene Vinyl Acetate

A high density polyethylene modified by the addition of vinyl acetate.RT

European Integrated Railways Radio Enhanced Network (EIRENE)

PanEuropean development project for a train radio system suitable for transmitting the information required by ERTMS.  Uses GSM in the 900MHz band allocated to railways.UoS

European Rail Traffic Management System (ERTMS)

High level set of standards to allow interoperability and effective management of Trans European railway operations. Previously, there was no distinction between the management aspects and the technical solution, European Train Control System (ETCS).UoS

European Train Control System (ETCS)

The signalling equipment aspect of ERTMS with its three levels of train control.  The Level 1 is effectively a standardised ATP system with line side signals.  Levels 2 and 3 require output from project EIRENE to assure transmission of movement authority by radio.UoS

EuroSPIN European Seamless Passenger Information Network

An EC funded project led by W S Atkins to develop an intelligent system which provides uptodate, multimodal passenger transport information to the public.RT

Examining Engineer

A person who is competent in the examination, assessment and maintenance of bridges to the satisfaction of the Zonal Civil Engineer.RT

Executive Grade

Old style executive job grading system.RT

Expansion Joint

A joint provided in CWR to allow rails to expand and contract as the temperature changes without buckling or rail breaks occurring. UoS

Expansion Shim (rail)

Spacer inserted between ends of abutting rails while track is being laid to provide allowance for the expansion of the rail steel when the temperature changes.UoS


Facing Point

Lock a device to ensure that points that allow trains to change route without reversing are locked in position.RT+UoS

Facing Points

Points where two routes diverge in the direction of travel [compare with trailing points].RT

Fail Safe

Design philosophy which results in any expected malfunction or failure maintaining or placing the equipment in a safe state.RT+UoS

Faregate (US)

Part of an automatic fare collection (AFC) system where the device is placed at station entrances and exits to regulate access by reading a ticket inserted by the passenger and restricting access if the ticket is not correct.  Various types are in use around the world to prevent passenger fraud and to permit the handling of large numbers of passengers with a minimum of staff.  (UK: Ticket Barrier / Ticket Gate)UoS

Fares Incentive Adjustment Payment

A modification to the fare cap to take into account the punctuality and reliability achieved by the TOC.RT

Fares Increase Regulatory Mechanism

A computerised system commissioned by OPRAF to check TOC compliance with the fare capping regime.  RT

Fastener, TiePlate

A special tieplate long enough to support the bases of a guard rail and the adjacent running rail and with a rail brace riveted to it for supporting the guard rail.UoS

Fastenings, Auxiliary Track Spring

Washers, tie plates, rail braces, rail anchors and other accessories.UoS

Fastenings, Track

A term commonly applied to splice bars, bolts, clips and spikes.UoS

Fault Reporting and Monitoring of Equipment System

Allows operators in Fault Control to record Signals & Telecommunications faults.RT


A structured process that identifies the engineering options and their implications including environmental issues.  It culminates in a feasibility report and a design development proposal.RT

Feasibility Study

A structured process that identifies the engineering options and their implications including environmental issues.  It culminates in a feasibility report and a design development (and, sometimes, implementation) proposal.RT


Slang term for the row of five white lights mounted at an angle above a (cleared) colour light signal to give an indication of the route set.RT

Feeder Station

A building or compound containing electrical switch gear and equipment to which main supplies from an electricity company are brought and from which the OLE or third rail is supplied.RT

Field Reporting Procedures

The instructions issued on how to report to TOPS for any particular location.RT

Finance and Business Information System

A homonym of FBMIS and which is now known as BMIS.RT

First Filament Failure

This refers to a failure in a signal lamp, which has more than one filament for enhanced availability.  The bulb must be replaced, but the signal still works normally and cautioning of trains is not necessary.RT

Fish Plate

Device to secure the ends of two rails together (in jointed track).RT

Fish Plate

Shaped and drilled (4 or more holes) steel plate used to link two rails.  Fishplates are bolted to the rail ends by using the space in the web of the rail of jointed track.  UoS+RT

Fishing Space (US)

Space between head and base of a rail occupied by a splice bar (angle bar, joint bar).UoS

Fishing Surfaces

Inclined surfaces under the railhead and above the rail foot that allow the fishplate to perform its function of aligning the adjacent pieces of rail.UoS

Fixed Asset

An item by the use of which the company generates income.  This may be a tangible asset or an intangible asset, such as software.RT

Fixed Distant Signal

A distant signal that is only capable of displaying a caution.RT

Fixed (Signal)

(1) A signal which is incapable (permanently or temporarily) of being cleared.
(2) A lineside signal which is always there as opposed to a (portable) hand signal.RT

Flagman (US)

The rear brakeman.  The great country music singer Jimmie Rodgers used to brag about being a flagman.  Reason?  Because flagmen had to know how to read so they could understand train orders.UoS


One of the consequences of rolling contact fatigue, resulting from the propagation of cracks underneath and parallel to the surface of the rail head or running surface of the wheel.  The phenomenon is more pronounced on rails where the traffic is predominantly in one direction. Railhead damage takes the form of pieces of the rail or tread surface becoming detached or being torn off.  The severity of the damage caused by flaking is generally felt to be less than that associated with shelling and spalling.  However, this is a largely qualitative form of differentiation.  UoS


Raised part of the rolling surface of the wheel used for guidance in tight curves and when travelling through the crossing parts of turnouts (points) without a moving frog (see also wheelset)UoS

Flange Way

Space in the crossing of a turnout (points) or diamond crossing that allows the flange of the wheel to cross the stock rail.  Space between the running rail and guard rail or the decking (timber or proprietary design) in road crossings to provide clearance for the passage of wheel flanges. UoS

Flare Opening (US)

Horizontal distance between the gauge line of the running rail and the side of the head of a guard rail or crossing wing rail at the widest part of its flared end.UoS


The railway equivalent to a puncture. Damage caused to the surface of a wheel, normally the result of sliding or skidding; can only be corrected by using a wheel lathe to restore the correct shape.RT

Flat Bottom Rail

Rail which is used in all modern track relaying.RT

Flexibility Premium

A percentage allowance paid to Relief Signalmen and Crossing Keepers to compensate for their travelling to and from places of work and the unpredictability of shifts.RT

Floating Slab Track

A track system using a concrete base mounted on rubber pads or resilient mats to reduce noise and vibration transmission to adjacent properties.  Some systems use steel and rubber spring suspended floating slabs to facilitate later changes.  UoS

Flow of Metal (rail)

Rolling out of steel on the crown of a rail toward sides of the head.  More common on the low side of a canted curve, located where trains travel frequently at less than balancing speed.  (UK: Lipping)UoS

Flow Separation

Loss of continuity of airflow along parts of the train’s outer surface.UoS

Fog Signal

See Detonator.RT


Material provided between the ballast and the subgrade to either increase or reduce the stiffness of the subgrade, or to prevent overstressing the subgrade.  Some use the term to describe embankments and similar structures which are not part of the preexisting ground.RT+UoS

Four Foot (UK)

The space between the running rails measured from the edge of the baseplates underneath the rails (rail chairs).  The most dangerous place to be on a railway.UoS

Four Rail System

A now almost unique current collection system used by London Underground which has separate positive and negative current rails.  The same system was used by the LNWR and the Mersey Railway at one time.  The usual 3rail method of conducting the return current via the running rails is replaced by a fully insulated system using separate positive and negative rails.  Originally used to reduce the risk of stray currents causing damage to nearby utilities and structures through electrolysis.  The system has the disadvantage of requiring special fault detection as earth faults do not cause current to switch off automatically (see also: conductor rail).UoS


The Federal Railroad Administration.  An agency of the U.S.  Department of Transportation with jurisdiction over matters of railway safety and research.UoS

Fracture, Detail

A progressive transverse fracture originating in the head of a rail, caused by inclusions in the original metal.  Cleaner steels means this flaw is on the decline.  (UK: Tache Oval)UoS


An agreement between the Franchising Director and a train operator to run particular passenger services for a defined period.RT

Franchise Director

Officer appointed under the Railway Act 1993 to franchise passenger services.RT


A device for detecting trains approaching level crossings without the use of a treadle.  Unfortunately, vulnerable to leaf contamination, and so being replaced by treadles.RT

Freight Upgrade

An initiative to secure future freight revenue and to protect passenger revenue, through infrastructure gauge improvements and routing strategy, particularly on the WCML.  RT

Frog (US)

A track structure used at the intersection of two running rails to provide support for wheels and passageways for their flanges, thus permitting wheels on either rail to cross the other.  (UK: Crossing)UoS

Frog Angle (US)

Angle formed by intersecting gauge lines of the rails, or by tangents to the gauge lines at their point of intersection when the frog is curved.  (UK: Crossing Angle)UoS

Frog Number (US)

Onehalf the cotangent of onehalf the frog angle, or the number of units of centreline length in which the spread is one unit.  The rate of spread of the gauge lines at the frog.  The number of units of length for a spread of one unit.UoS

Frozen Joint

A joint so tight that the rails cannot move as temperature varies.  UoS

Fuel Oil

Diesel and other similar hydrocarbon based oils used as a fuel for train motive power.RT


Gain Amplification [especially of a signal].RT


Flexible structure provided at vehicle ends where necessary to provide access from one vehicle to another.  The gangway is divided between the two adjacent vehicles and is normally closed off when the vehicles are uncoupled.UoS

GasTurbine Electric Locomotive

A power unit in which a gas turbine drives electric power, normally alternators supplying current to electric traction motors on the axles.UoS


The distance between the inner running faces (gauge lines) of the two rails, on the same track.  Also used to describe the "envelope" through which trains’ profiles must fit this is the structure gauge (US spelling "gage".RT+UoS

Overview of Common Track Gauges:

Broad gauge (Spain): 1674 mm 5'5 9/10th"
Broad gauge (Portugal): 1665 mm 5'5 11/20th"
Broad gauge (Ireland): 1600 mm 5'3"
Broad gauge (Finland): 1524 mm 5' exactly
Broad gauge (former USSR): 1520 mm 5'
Standard gauge (Worldwide Application): 1435 mm 4'8 1/2"
Narrow gauge (Cape gauge): 1067 mm 3'6"
Narrow gauge (meter gauge): 1000 mm 3'3 37/100"
Narrow gauge (Latin America) 950 mm  
Narrow gauge (Austria): 750 mm  

Gauge Line

A line five eighths of an inch, about 15mm below the running surface of a rail on the side of the head nearest the track centre; the line from which measurements of gauge are made. Gauge, narrow (see Narrow Gauge.)UoS

Gauging (of track)

Bringing two opposite rails into their correct relative positions as regards to their distance apart.UoS


A system for resource control of multipleunit trains.RT

Gemini for Non Integrated Unit Stock

A Windows frontend facility for Resource Controllers to manage the day to day operation of their fleets.  Adopted by Virgin Trains.  Users of GENIUS withdraw from TOPS/POIS/EDTA.RT

General Purpose Radio System (GPRS)

Implementation of PSS using mobile radio communications.UoS

General Utility Van

A type of parcels van, some of which were converted by Railtrack for leaf fall track clearance.RT

Geographic and Infrastructure Systems (GEOGIS)

A major database of railway infrastructure assets containing information on the physical location of track, buildings and structures.RT

Geographic Information System (GIS)

High quality database for assets using exact geographic information for object location, in most cases referenced to a national grid system.  May include full mapping information.  Generally of a relational type and based on a standard software such as ORACLE or ARCINFO.UoS

Global Positioning by Satellite (GPS)

Navigation based on measuring time delays of signals received from four or five satellites.  See also DGPS.UoS

Global System for Mobile Communications (GSM)

Internationally agreed standard and protocols for mobile radio (telephone type) communications using cellular arrangements to maximise use of the frequency spectrum.  European standard. UoS

Global System for Mobile Communications for Railways (GSMR)

Specialised GSM cellular Personal Mobile Radio (PMR) implementation for railways using the 900MHz band and with a higher level of reliability and safety and more features than GSM.UoS

Goods Line

A line which has not been signalled to the standards required for running passenger trains.RT

Grade US

Term for sloping track.  UK terms are gradient or "bank".  "At grade" means level track. UoS

Grade Crossing (US)

See level crossing.UoS

Grade Line (grade)

(1) The line of a profile representing topofrail elevations of the track. 
(2) A series of staked elevations transferring this line to the ground or roadbed.UoS

Grade Rail

The rail first surfaced to track elevation; the line rail on tangent track, the inner or low rail on curves.UoS

Grade Separation

A term applied to the use of a bridge structure and its approaches to divide or separate the crossing movement of vehicular, pedestrian or other traffic, by confining portions thereof to different elevations.  See Flyover and Dive under.UoS

Green Zone

An area of protection for workers, which separates work on the railway line from train movements. The simplest way of arranging such a zone is to stop movements of all trains on all lines at the location concerned.  Fencing off the work area may be an accceptable alternative but requires reduced speed operation.  .RT


Slang term for a train enthusiast.RT


Slang term for a special train, often a steam special.  The word is derived from ‘gricer’ and ‘x’ meaning excursion.RT

Gross Project Code

Records the full amount of income invoiced by a business unit to a customer prior to allocating income to the interunit account code of the appropriate business unit.RT

Ground Disk

Small shunting signal at low level (often called a "dolly" or a "dummy").RT

Ground Frame

A small lever frame to operate points and signals, usually mounted at ground level.  Sometimes a small switch panel which works little used connections at locations remote from a signal box.RT

Ground Position Light

A low level shunting signal displaying lights rather than a disc.RT

Group Standard

A document published by the Safety and Standards Group of Railway Safety as a Railway Group Standard or a Railway Group Code of Practice.RT


Senior Conductor, Conductor or Train(wo)man.RT

Guard Rail (US)

See also: Check Rail.  Guideway (UK) Running surface with mechanical or electrical guidance function for nonrail guided transport.  (US) Supporting structure for a rail track. UoS


Hackwall (US)

The section of wall rising from the surface of an abutment.UoS

Hand Points

Turnout (points) which is worked manually by an adjacent independent lever.RT

Handite Hand Held Sandite Applicator

(a trade name used by Chipman Rail).RT


Means harm to the health of living organisms or other interference with the ecological systems of which they form part.  Also, in the case of man, includes offence caused to any of his senses or harm to his property.  Harmless has a corresponding meaning.RT


Situation with potential to cause harm or loss.RT


Training course for drivers of vehicles carrying dangerous substances in packages.RT

Head Block (switch) (US)

A pair of ties (or, in old types of turnouts, a single tie) used to support the switch points operating mechanism and the switch stand.UoS

Head Code

An obsolete term for the Train Reporting Number.  The headcode is a unique code to identify each train; it is made up from the Class of train, followed by its destination; and finally its number designated by track access (eg.  1A30 = a Class One express train, travelling towards London, No.  30).  The range of letters used in the train reporting numbers are too detailed to list here.RT

Head Rod (US)

The switch rod nearest the toe of a switch, usually placed between the two head block ties.UoS

Head End Power

A system of furnishing domestic electric power (hotel power) for a complete railway train from a single generating plant in the power unit, excluding traction power.UoS

Headspan Wire

A wire suspended across the tracks and from which the OLE is suspended.RT


The time interval between the passing of the front ends of successive multiple units or trains moving along the same lane or track in the same direction. UoS

Heater, switch

A device for melting snow at switches by means of steam, an electric current, gas jets, or oil.UoS

Heat Treated Rail

Rail subjected to accelerated cooling or other heat treatment after rolling with the intention of achieving specified mechanical properties.RT

Heavy Haul Railway

large capacity train haulage of bulk commodities.  Normally uses unit train format.UoS

Heavy rail transit

A mode of rail rapid transit generally characterised by high passenger carrying capacity , fully gradeseparated construction, operating on exclusive rights of way, and station platforms at the floor level of the vehicles.UoS

Heavy rail vehicle

A vehicle operating on a heavy rail transit system.  Typically, electrically propelled, bidirectional, capable of operating in multiple unit, and designed for rapid, highlevel boarding and discharging of passengers.UoS

Heel Block (switch)

A block which spans joints and fills the space between adjacent rails at the heel of a switch, joined with outside splice bars by continuous bolts to form a unit joint.  Also serves as a foot guard.UoS

Hertzian Contact

The pressure distribution in the contact patch.UoS

High Speed Interoperability

Requirement placed on highspeed rolling stock and operational practice to allow cross border operation without locomotive and new changes. UoS

High Street Environment

A worksite outside the area of an Infrastructure Manager’s (Network Rail’s in Britain) Controlled Infrastructure and which may not impinge upon railway operationsRT

Highway Crossing Protection (US)

An arrangement of one or more highway crossing signals, with or without gates, to protect highway traffic.  (UK: level crossing protection)UoS

Hollow Bearer bearer (Sleeper)

, fabricated from steel or cast, with space internally to accommodate switch drive mechanisms and detection devices.  Can also be used to route cables across a track.UoS

Home Signal

The first stop signal on the approach to a (non Track Circuit Block) signalbox.  See Track Circuit Block.  RT+UoS

Hot Axle Box Detector / or Detected

This is a trackside temperature detector, which warns a signal box of an overheated bearing; as it counts the passing wheels and indicates which axle is faulty, if one axle or wheel is hotter than the others on the train.RT

Hotel Power

That part of a train’s power consumption which is needed to power air conditioning, lighting, heating and kitchen facilities on a train.  Often greater than 1020% of the total energy requirement.  UoS

House Track (US)

A track alongside of or entering a freight house; used for cars receiving or delivering freight at the house.  (UK: industrial sidings)UoS

Human Resources System

A computer system replacing NPS and PEARLS.RT

Hunting (UK)

The sinusoidal oscillation of a bogie or wheelset at speed caused by wheelset conicity and yaw stiffness and initiated by irregularities in the track or wheels.  Different designs "hunt" in different ways and under different conditions.  Below a critical speed, the oscillations decay away.  Above the critical speed the oscillations increase, and this can have a damaging effect on rails or may lead to the train being derailed.  Suspension design often affects ride as much as anything and the whole science of bogie design can be a bit of a black art.  (US: boxing) UoS



System Monitor a facility for reporting errors to the Integrated Electronic Control Centre.RT

Impact Coefficient

An enhanced loading designed to simulate occasional exceptional or accidental loads to which a sleeper may be subjected in serviceRT

Impedance bond

An electrical circuit at installed at points on the track where track circuit frequencies or codes change in electric traction areas to separate signal and traction current.  (See also: Bond)UoS


The undertaking of physical works to deliver the detailed design.RT

Improved Manufacturing Performance Through Active Change and Training

A Westinghouse partnership initiative.RT

In Advance Of

Ahead of in the (normal) direction of travel.RT

In Rear Of

Behind in the (normal) direction of travel.RT


An unplanned event which, under different circumstances, could have resulted in:

  • physical harm, injury or disease to an individual;
  • damage to property;
  • a near miss;
  • loss;
or any combination of these effects.RT

Insulated switch

A switch in which the fixtures, principally the gauge plates and the switch rods connecting one rail to the other, are provided with insulation so that electric currents will not be shunted.  Also, the turnout rail must contain an insulating joint.UoS

Insulating rail joint

Sometimes called Insulated Joint.  A rail joint designed to stop the conduction of electric current between two lengths of rail, as at the end of a track circuit.  Normally consists of insulated fishplates, end postand insulating sleeves for the rail bolts.UoS

Integrated Electronic Control Centre (IECC)

Train control centre (power signal box) with responsibility for a hundred or more route km where all data displays and most safety interlocking are computer controlled.  Many functions are carried out automatically using train describers and automatic route setting (ARS) based on TRUST Train Ids.  Operators are only involved in situations where there is disruption.  IECCs exist at London Liverpool St., Merseyside, Tyneside, York and elsewhere. UoS+RT


An operator of privately owned wagons.  RT


In signalling, a system to prevent the setting up of conflicting routes by logically linking points and signal operation.  At first interlocking of actions was achieved mechanically through the locking frame, then electromechanically by relays in the signal box.  Now, interlockings are largely computerised using a two in three voting system, diverse hardware and software or protocols.  Also note the term SSI (solid state interlocking).  Computer hardware and software must be safety approved.  In the US, the term Interlocking refers to an area where junctions and signals are under the control of a signal cabin or "Tower". UoS+RT

Intermediate Block Home (IBH)

Signal stop signal controlling one exit from the section in the rear into the block section ahead, originally at an intermediate section signal box.RT+UoS

Intermediate Block Section

A track circuited section of line between the section signal and the Intermediate Block Home Signal, both of which are worked from the same (Absolute Block) signal box.RT

Intermittent ATP (IATP)

System of automatic train protection where trains receive information from the trackside at regular intervals.  In between these fixed locations, trains cannot receive any updates.UoS

Intermodal Car

A rail wagon designed specifically for handling piggyback trailers or containers, or both.UoS

Intermodal Traffic

Freight moving via at least two different modes of transport, e.g., trucktorail.UoS


The actual difference in time between trains.RT

Invitation To Tender

A collection of documents issued to one or more potential suppliers or contractors to invite commercial bids to undertake specified tasks.RT


A test coach operated on the railway to test the strength of radio signals received via the National Railway Network Radio system.RT



The rate of change of acceleration with time. Units are mass per time cubed.  Passenger comfort criterion. Maximum level allowed in the UK is 0.7m.s3. UoS


The junction of two rails or of like materials in bridge members.  UoS

Joint bar (US)

A steel angle bar or other shape used to fasten together the ends of rails in a track.  They are used in pairs, and are designed to fit the space between head and flange (fishing space) closely.  They are held in place by track bolts.  Also, called angle bar, rail joint bar, and splice bar. (UK: fishplates)UoS

Joint Industry Cost

Costs incurred by Network Rail on behalf of customers and "passed through" to them.RT

Joint Line

Any route where the line was formerly owned by two or more companies.RTWP

Joint Line

The route from Doncaster to Peterborough via Lincoln and Spalding; its title when built was the Great Northern and Great Eastern Joint Railway.RT

Jointed Rail or Track

A method for joining lengths of rails with steel members (fish plates) designed to unite the abutting ends of contiguous rails.  Normal length of 60 ft but can be 45 or 30 ft lengths.UoS+RT

Journal Entry

Debit or credit to a general ledger account with a balancing debit or credit to another general ledger account.RT


Key Performance Indicators

These are financial or other indicators used to monitor how well the business is doing in terms of satisfying its Critical Success Factors (order qualifying and order winning criteria.)RT

Kinematic Envelope

The volume of space swept through by a train in motion.  It takes account of overhang on curves, tilting, etc thus differing from the static loading gauge The kinematic envelope must be smaller than the structure gauge.RT+UoS


Ladder Track

A track connecting successively the tracks of a yard.  UoS

Lateral Track Force

Sideways force on the track generated by a vehicle on a curve.UoS

Lead Business Unit

The business unit responsible for sending an invoice for all services to a TOC, regardless of which business unit will ultimately recognise the income.  RT

Lead track

An extended track connecting either end of a yard with the main track.  UoS

Leeds Northern

Slang title given to the line between Northallerton and Eaglescliffe.  This line ran from Wortley Junction through Horsforth, Harrogate, Ripon, Northallerton, Eaglescliffe, Stockton, Hartlepool and Sunderland to Newcastle.  It was owned and operated by the "Leeds Northern Railway" from 1847 until 1854, when it was taken over by North Eastern Railway (NER) but (surprisingly) Leeds Northern title lives on in everyday railwayman’s language.RT

Level Crossing (UK)

The point where a railway line and a motor vehicle road intersect at the same level. Protection levels include (i) signage, (ii) road traffic signals, (iii) flashing lights, (iv) automatic half barriers, (v) automatic full barriers, (vi) manually operated barriers.  Level crossings may be monitored locally or remotely using CCTV etc. (US: Grade Crossing).UoS

Lever Collar

A device, often of carved wood, placed over a signal lever or other control to remind the operator of it being restricted or out of use.RTWP   See also Reminder Appliance.RT

Licensed Operator

A company or organisation who is granted a licence by the Rail Regulator to operate rail services, and to operate vehicles on the track, under terms and conditions defined by the Rail Regulator.RT

Light Loco

Term used to describe a locomotive running on its own without a train (usually to or from a depot for maintenance etc.  (sometimes called a Light Diesel or Light Electric, according to type)RT

Light Rail Transit

A mode of rail transit characterised by its lower passenger carrying capacity and the ability to operate on its’ own rightofway (reservation, side or central) or to share road space with other traffic.  Nowadays light rail vehicles (LRVs) are much favoured as an alternative to full blown subway or underground (heavy metro) lines for urban rail systems due to their reduced construction costs.  Passengers may board or alight from track level or using vehicle floor level platforms.UoS

Light Rail Vehicle (LRV)

Modern generic term for tram or streetcar.  An electrically powered rail vehicle using rails embedded in the roadway (operating in mixed traffic ) or using dedicated rail tracks, or a combination of the two as in Manchester, Sheffield, and many other European and US cities. Modern LRV design concentrates on low floor construction to make access easier for passengers and to reduce the height of platforms at stations.  Much innovation is appearing in the industry as a result.  Apart from recent developments in Germany, LRVs are electrically powered , generally from overhead supplies. UoS

Light Steam

Sufficient steam pressure to work injectors, lubricators and brakes but not more than 75% of maximum boiler pressure.RT

Like For Like Renewal

The removal and restoration or refurbishment of an item where the work does not require any fundamental design change to the Infrastructure.  This may involve restoring or refurbishment of the original item or replacing it with an operationally equivalent new item.RT

Limit of Movement Authority (LMA)

The instantaneous distance that a train can travel before encountering a stop signal.  UoS

Line Capacity

The maximum possible number of trains capable of being operated over a line in one direction. Usually expressed as trains per hour.  The theoretical (maximum) capacity will depend on the trains running speed and braking capacity and on how the signalling is arranged. UoS

Line Light

An indicator on the drivers desk of an electric train that current is being drawn from the overhead wires.  When the line light is lost (and cannot be reset) it is an indication that there may be a fault with the pantograph or overhead wires; this requires immediate attention to avoid serious damage.RT

Line Rail

The rail on which the lateral track alignment is based; the east rail of tangent track running north and south, the north rail of tangent track running east and west, the outer rail on curves, or the outside rails in multiple track territory (US definition).UoS

Line Standard

See Network Rail Line Standard.RT

Lining Track

Shifting the track laterally to conform to established alignment.  Maintenance lining is ordinarily done during repairs; general lining is done to make the track conform throughout to predetermined alignment.UoS

Link Up

The independent organisation which administers the Railway Qualification System and QLink on behalf of Network Rail.RT


Situation where the rail surface experiences excessive lateral forces or, in the case of a rail joint, longitudinal forces.  This results in the rail steel being pushed and extruded over the edge of a surface.UoS

Liquidated Damages

Financial compensation from a contractor for loss incurred as a result of his default.RT

Loading Gauge

The dimensions of height and width which must not be exceeded by a rail vehicle or its load, so as not to foul lineside fixtures or structured.  Similarly, the dimensions in respect to the rails which must not be infringed by such structures (structure gauge).  See also Kinematic EnvelopeRT

Local Procurement Agent

The individual employee in most departments throughout Network Rail who has delegated procurement authority for a range of low value purchases.RT

Locking Bar

Metal bar connecting the switch blades to the point locking mechanism to prevent the points from moving as a train passes through the turnout.  The locking bar is usually connected to a cammechanism.UoS


A self-propelled, nonrevenue rail vehicle designed to convert electrical or mechanical energy into tractive effort to haul trains of nonpowered carriages and freight cars.UoS

Long Welded Rail

Usually delivered to renewal sites in 300ft or 600ft lengths (also known as CWR continuously welded rail.)RT

Long Welded Rail Train

The vehicle used to deliver LWR to the work site.  RT

Longitudinal Timber

Large cross section baulk of timber used on some bridges and positioned under each rail longitudinally.  It acts as a beam and is the securing point for baseplates.  Also used to support rails along the edges of pits in depots.


A siding with a connection to the running line at each end, used to enable a locomotive to run round a train or to allow a slower train to be overtaken by a faster train.RT

Lubrication, Flange

One of the critical areas of wear on railways occurs at the point of contact between wheel flange and railhead in curves.  This wear reduces the flange profile and, if allowed to develop, can cause derailment.  It also damages the inside edge of the rail head, potentially leading to gauge corner cracking. The wear can be reduced by lubrication of the contact area.  The lubrication system may consist of flangeactuated track mounted lubricators at the entrance to curves or trains may be fitted with onboard flange lubrication.  The Paris Metro, for example, used a train-mounted lubricator which was actuated by links on the bogie which detected the change in angle as it turned onto a curve and injected a small amount of oil onto the wheel.The risk with flange lubrication is over application.  This will leave lubricant on the wheel tread or railhead and results in sliding during braking.  One such celebrated occasion occurred on London's Victoria Line some years ago, which resulted in 35% of the trains being unserviceable due to out of round wheels damaged by sliding.  UoS



Magnetically levitated vehicle or train of vehicles with guidance and propulsion provided by magnetic forces.  Support can be provided by either an electrodynamic system (EDS) whereby a moving vehicle is lifted by magnetic forces induced in the guideway, or an electromagnetic system (EMS) where the magnetic lifting forces are created by actively energising magnets in the guideway.UoS

Main Aspect

The red, yellow, double yellow, flashing yellow, flashing double yellow or green aspect of a colour light signal.RT

Main Line

The (any) running lines in two track section.RT

Main Line (UK+US)

The principal line or lines of a railway as opposed to branch lines (UK: also known as trunk route).  Sometimes used to refer to the fastest line(s) in a multiple track area.  UoS

Main Track (M.T.) (US)

A track extending through yards and between stations upon which trains are operated by timetable or train order or both, or the use of which is governed by block signals.  (UK: Main Line)UoS


A measure for the ease with which a piece of equipment or a system can be brought back to the fully operational state after an inservice failure or when being serviced.  Indicators can include Time To Repair and Time To Replace (TTR).UoS


The activity of returning an asset to a condition where it can safely and reliably perform its function.  See also Preventative Maintenance Reactive Maintenance, Reliability Centred Maintenance and Remote Condition Monitoring.UoS

Margin Book

A reference book defining the characteristics of each TRUST reporting point on the zone in relation to data accuracy requirements.RT

Mark 1

The original British Railways passenger vehicle design of the 1950s which was constructed using an underframe and a relatively light superstructure.  Now only RES parcels vans, some charter sets and some electric multiple units operated by South West Trains, South Central and Connex are of the Mk1 type.  The "Mark" no.  refers to the basic type of stock.RT

Mark 2

Integral body shell design passenger coaching stock which was built in the late 1960s and early 1970s. Virgin Cross Country, Great Western, Anglia and West Coast use such rolling stock for locohauled trains only.  The "Mark" no. refers to the basic type of stock.  RT

Mark 3

Integral body shell design passenger coach and HST trailer cars.  The "Mark" no.  refers to the basic type of stock.  RT

Mark 4

Describes the type of coaching stock used for the InterCity East Coast electric trains which had originally been built for tilting operation but was not fitted with the necessary mechanism.  The "Mark" no.  refers to the basic type of stock.  RT+UoS

Marker Board

A doublesided yellow board with two vertical redyellow flashing lights on one side and two yellow flashing lights on the other used to indicate a work site (possession).  From August 1999 there have been two types: i) Possession (red lights); ii) Work Site (yellow lights). Possession and work site are not necessary the same. RT

Marshalling Yard (UK)

A number of sidings in a particular arrangement which are used to split and reform freight trains.  Trains arrive in reception sidings and the individual wagons are distributed into classification sidings using a hump or shunting.  Reformed trains are moved to departure sidings where they are collected for onward movement.  Very common in US and some continental European countries but not in UK.  (US: Switching Yard)UoS


A word used in procedural documents to express a permitted practice or action.  Compare with shall, should, must, will.RT

Measured Shovel Packing

A track maintenance procedure where gravel is placed underneath individual sleepers to restore track top without disturbing the underlying ballast. Stoneblowing is the mechanised form of this method of treatment.UoS

Mechanical Points

Points (turnouts) which are operated without any form of power operation.RT


(1) Property management and accounting system, holding a database of property related information and providing a full range of financial and management accounting functions or (2) an overhead line test coach operated by AEATRail at Derby.RT

Merry Go Round

Coal supply train from colliery or other bulk loading point to a power station, always in the same configuration.  RT+UoS

Messenger Wire

See Catenary. UoS


The term used to denote an urban railway running exclusively on its own right of way, often partly or wholly underground, carrying large numbers of passengers on trains at close headways.  In the US synonymous with the term "subway".  The word is a diminution of the Metropolitan Railway of London, the first urban underground railway in the world.  It has since been adopted by many transport authorities to give a catchy name to their system, even if not strictly correct.UoS

Mill Heat Treated Rail

Rail subjected to accelerated cooling or other heat treatment after rolling, with the intention of achieving specified mechanical properties.RT

Mini Marpas Maintenance and Renewal

Planning System used by BR Research to derive track usage rates for new vehicle types as they are introduced onto the network.RT

Minutes Average Performance

A database of train delay costs.  RT

Motor Bogie

A powered bogie.  The term is usually confined to multiple unit trains so as to distinguish them from trailer (unpowered) bogies.  Some railways operate trains with all bogies motored.  See also "bogie". UoS

Motor Car

A passenger vehicle in a multiple unit train which is provided with traction power equipment.  UoS

Moving Block Train Control

The provision of a full braking distance between trains, based on the line speed rather than the speed of individual trains, limits track capacity.  A first approach to increasing the capacity of a railway line is to provide a braking distance based on the current speed of a train and not that given by the line characteristics.  This is described as moving block signalling. See also Relative Braking Distance.UoS

Multilingual Automatic Inquiry System

A project proposal to provide passenger timetable information in the local language.RT

Multiple Unit (MU)

A term referring to the practice of distributing traction power to units along the length of the train and for coupling two or more power units.  MUs can be EMU (electrical) or DMU (diesel).  UoS

Multi SPAD

Signal a signal that has been passed at danger (as defined in category A) more than once in 12 months or three or more times in any three year period.RT


A word used in procedural documents where compliance with legislative or regulatory requirements is obligatory.  Compare with shall, should, will, may.RT


Nairns Programme

Work on the reprofiling of farm crossings to improve adverse gradient profiles and associated work.RT

Narrow Gauge

A gauge narrower than standard gauge.  A gauge of 24 inches or less is commonly employed for industrial railways.  Meter gauge is often used in territories at some time under the influence of Germany and France while UK influenced areas would be dominated by 3ft6in tracks (1067mm).UoS

National Railway Academy (NRA)

Superseded concept for a national organisation to offer, deliver and validate railway oriented training and education.UoS

National (Railway) Radio Network (NRN) VHF (200 MHz)

General purpose cellular radio type network (nonsecure). Used for RETB with a secure protocol.UoS

Network Rail

The not-for-profit company that maintains and enhances most railway (not Metro) wayside infrastructure in UK, created when Railtrack was put into financial administration.  Network Rail bought the assets of Railtrack in spring 2003.  Some harbour railways are responsible for their own track.UoS

Network Rail Energy Database

A bespoke computer system operating on a Microsoft Access database.  Each Network Rail zone operates the system in the Finance department, and HQ Procurement operate a master system with an aggregate of data of all Zone and HQ departments.RT+UoS

Network Rail Line Standard

A standard published by a directorate of Network Rail as a Network Rail Line specification, Network Rail Line procedure or a Network Rail Line code of practice,.  Its alphanumeric identity is prefixed by RT/, followed by a letter designating its directorate.RT+UoS

Neutral Section

A short insulated section of the overhead line to separate electrically one part of an electrified railway line from another part, e.g., to change from one supply authority to another.  Isolation has to be maintained during the passing of the pantograph.  Also used in power supply management and fault mitigation.  UoS+RT

New Line

A term sometimes used for the Hertford loop, which is newer than the main line via Welwyn.RT  Also used for the DC electrified lines between Euston and Watford.RTWP


The trading name for the Tyne & Wear Passenger Transport Executive (which is no longer a transport operator in its own right.)RT

Northern City Line

The line from Drayton Park to Moorgate which is the only DC electrified line on the Eastern zone.RT

Number, turnout

The number corresponding to the angle of the crossing used in a turnout.  In the UK frogs are lettered from A (steepest) to G (shallowest).UoS


Occupation Bridge

A bridge carrying a private road which pre-existed the railway.  User rights for the bridge are generally as for the road it carriesRT

Occupation Crossing

A level crossing which does not carry a public road, but one which leads to a farm, factory etc..RT


Term used when a signal is in the cleared position (e.g., the Distant is "off".)RT

Office of Passenger Rail Franchising

The organisation which funds unprofitable passenger services and allocates franchises to TOCs.RT

Old Road

The line between Rotherham and Chesterfield bypassing Sheffield, so called because it was built before the latter line.RT


Term used when a signal is displaying its most restrictive indication (e.g., the distant signal is "on".)RT


Total project cost less design and implementation cost.RT

One Train Working (OTW)

Of signalling on a single line, with or without a train staff, where only one train at a time is permitted.RT

Open Access

The process by which new train operators may gain access to the railway infrastructure, provided they meet specified safety and other standards. RT

Operationally Equivalent

A replacement item which is functionally identical to the item it replaces, albeit with physical or cosmetic differences.RT


The computer system used to divide revenue from ticket sales between train operators.RT

Originating Unit

The business unit responsible for posting an interunit journal entry to move income or cost from one business unit to another in order to match income with costs.  RT


Place at which one drainage system discharges into another drainage system or watercourse.RT

Outline Project Specifications

A document listing the principal elements of proposed signalling works. RT


Based Contract a contract where the outputs and the price are defined, not the means to achieve the end result.  RT

Outside Party

An organisation or legal entity other than Network Rail.RT


A bridge crossing over the railway (Network Rail property).  This includes bridges for roads, footpaths, services or industrial use.RT+UoS


Generic term (as in "the overhead") referring to electric traction supply wires suspended over the track for current collection by trains.  Also known as "overhead line, OLE or OHLE (overhead line equipment) or catenaryafter the contact wire suspension system.  Current is collected by a pantograph on the roof of the train or locomotive, although trolley poles are still used on some tramways (e.g., Melbourne, AU). UoS


The section of line in advance of a stop signal which must be cleared by the preceding train before the next signal in rear of the stop signal can display a proceed aspect.  Practically, a short (about 200m) additional braking distance beyond a signal, provided in case the train fails to stop at the signal when it is showing a danger aspect.  On metros using the equiblock system, the overlap is usually a full block section long.  RT+UoS


P1 and P2 forces

Vertical impact forces occurring at dipped rail joints.  Maximum P1 force permitted in the UK is 350kN.UoS

P11D Generation System

A PC based facility for preparing P11D returns for the Inland Revenue and the individual forms for distribution to employees.RT

Packet Switch System (PSS)

Transmission of information (voice, data etc) over one or several routes, using short packages, each with a unique identifier, which are combined by the receiver to make up the full message.UoS


A database used to store train running information captured by the TRUST system Paladin is available to all rail industry users.RT

PALADIN Extract and Reporting System

A versatile train performance measurement facility, producing analysis reports focusing on train performance and delay attribution.RT


The device on the roof of an electric locomotive or multiple unit through which electric power is drawn from the overhead wires.RT

Pantograph, variable height

Traction current collection device mounted on the roof of a railway vehicle fed from an overhead supply system, usually featuring a carbon contract strip.  Nowadays, pantographs are sophisticated aerodynamically designed devices which can operate at high speeds and on tilting trains without loss of contact and with builtin safety devices which reduce the risk of damage to overhead wires in the event of a fault.  Under certain circumstances (high winds etc.) a pantograph may rise above the wire and can pull it down for considerable distances before this is noticed by the train crew and the train can be stopped. Modern pantographs are fitted with automatic detection and dropping devices (ADD), such a device can be created by using a hollow carbon collector strip on the pantograph.  This is connected to a pneumatic circuit which will trigger a switch if the air escapes when the contact strip fractures due to an impact.  Alternatively, the horns (curved ends) of the pantograph may be equipped with frangible pneumatic sensors which, if broken by a wire support, cause the detector system to lower the pantograph.  UoS

Parent Track (US)

A track from which a turnout is constructed.  A main track is the parent track as opposed to a passing track or spur, a ladder track is the parent track with respect to the yard tracks. Parental Guarantee a document signed by the holding company which owns the subsidiary company entering into a contractual agreement with Network Rail, where the holding company underwrites all potential liabilities of the subsidiary.RT

Parkway Station

A railway station with a large car park and easy road access.RT

Passenger Service Requirement Compliance Yardstick

A computerised system commissioned by OPRAF to check whether TOCs are meeting their Passenger Service Requirement.RT

Passenger Track Access Billing System

Which calculates track access charges for each passenger TOC, based on the tariffs for each service group and the record of all train movement details.RT

Passenger Transport Authority (PTA)

Committee of elected councillors which supervise public transport provision in a PTE area.  UoS

Passenger Transport Executive (PTE)

Professional management of public transport provision in a PTA area (e.g., Lothian, Greater Manchester, Merseyside, South Yorkshire, West Yorkshire, West Midlands). UoS

Passenger Trespasser

A person either travelling or intending to travel who is in a place on the operational railway where they are not authorised to be. RT

Passing Loop (UK)

A parallel length of secondary track provided in places where trains pass or overtake each other.  This may be provided in conjunction with a station.UoS

Pee Wee

A warning device for use by personnel on or near the line.RT


A BR Business Systems data extraction and analysis system that uses PALADIN data.RT

Performance Historical Information System

An older TRUST performance database, available via TRUST to authorised users.RT

Periodical Operating Notice

A Bimonthly publication which contains all current amendments to the books of Rules and Regulations and certain miscellaneous notices.RT

Permanent Way

Generic term for the structure of the railway track, referring to the rails, sleepers (ties in US), ballast, any blanketing material (including geotextiles) and associated drainage.  The term "permanent" arose to distinguish it from the temporary track laid during the construction of the railway.UoS+RT

Permanent Way Component

A constituent part of the structure of the track including assembly tools and fixtures (but excluding permanent signalling equipment other than stretcher bars of turnouts or points), track ballast and subballast material or drainage.RT

Permissive Working

Permits more than one train to be in the same signal section on the same line at the same time; can apply to some platforms.  Refer to Absolute Block as a contrast.RT

Person in Charge of Works

Responsible for ensuring the safety of staff working on the track or nearby.RT

Personal Track Safety (PTS)

A Network Rail certificate of competence which must be obtained to be allowed access to the Network Rail controlled infrastructure (trackside). The certificate requires attendance at a two day course and passing of a test.RT+UoS

Personnel Enquiries and Administration Recording

Local System used to maintain data about employees.RT

Phase 0

In NR WCML terms, period of interim and full running of ATT (active tilting train) on the WCML at existing line speeds.RT

Phase 1

In NR WCML terms, period of full running of ATT (active tilting train) on the WCML up to speeds of 200 km/h (125 mph) between 2002 & 2005.RT

Phase 2

In NR WCML terms, full service of ATT (active tilting train) on the WCML after April 2005 up to speeds of 225 km/h (140 mph).RT

Phase Break

A location where overhead wires are sectioned (see Neutral Section) to provide an insulated section between different sources of electric power.UoS

Physical Needs Break

A guaranteed break in a Driver’s turn of duty when he/she is free from duty.RT


The conveying of unaccompanied lorry trailers by train.RT


A man provided to accompany a train driver in certain circumstances, usually:

  1. The driver doesnot know the route or traction
  2. Temporary single line working is in operation and the Pilotman’s presence is essential to ensure that only one train at a time is on the single line
The terms Route Conductor or Traction Conductor are also used.RT

Pinch Point

A location on the rail network where the number of train movements is close to, or projected to exceed, the capacity of that location.RT


A Performance system which records the reasons for train delays, compatible with EGRET.RT

Platform, high

A passenger station platform at approximate car floor height.UoS

Platform, low

A passenger station platform at approximate top of rail height.UoS

Pocket track (US)

A special track connected to the mainline to allow storage of out of service trains.

Point Lock

(see Switch Lock).

Point Motor

A device used to move the switches (points blades).RT

Point of Switch, theoretical

The point where the gauge line of the switch rail, if produced, would intersect the gauge line of the stock rail.  Also called vertex.UoS


UK term used in the same way as the term turnout, denoting the sum of the infrastructure components (e.g., S&C) required to allow trains to change tracks.  Colloquial term for the switch rails in a turnout.  See page 52 for an illustration.UoS

Points and Crossings

An alternative abbreviation for S&C.RT

Points, Run Through

A movement which runs through a trailing set of points which are not set in the correct position for the train movement.RT

Portable Data Terminal

Used inter alia by signallers to input data to TRUST by attachment to a BRT telephone line.RT


Entrance to a tunnel or a type of overhead line support.RT


When a section of track is required for maintenance, repair or renewal and when trains cannot run, it is handed over by the operators to the engineers, who take "possession".  Special protective measures are used to prevent access by unauthorised trains.  The Engineer may run his own trains within the limits of the possession but no other trains are allowed to run within it and comprehensive safety regulations ensure that these conditions are maintained.  When the track is returned to the operators, the engineers "give up possession". UoS+RT

Power Box (UK)

Signal box controlling a large area using remote control systems to set routes in interlockings at remote locations (US: CTC).RT

Power Operated Doors

Doors on a train where the opening and closing is controlled by the Guard (or Driver in the case of a DOO(P)) train.RT

Power Operated Points

Points operated by a means other than mechanical (eg.  electric motor, hydraulics or compressed air).RT

Power Unit

A self-propelled vehicle, running on rails and having one or more electric motors that drive the wheels and thereby propel the consist to which it belongs, on an electric power unit.  The motors obtain electrical energy either from a rail laid near to, but insulated from, the running rails, or from a wire suspended above the track.  Contact with the wire is made by a pantograph mounted on top of the unit.UoS

Preventative Maintenance

Describes the activity of performing scheduled maintenance on the basis of experience with the objective of minimising the potential for inservice failures.UoS

Primary Authority

The authority granted by the Network Rail plc Board directly to named individuals or bodies to act on behalf of the Board.RT

Priority On Managing Performance Trends

A Railtrack initiative announced in early 1998.RT


A document that specifies or describes how an activity is performed.  It also identifies the what, when, where and who of the activity described.RT

Process for Performance Improvement

Performance management based on principle of delay budgeting. RT


(1) A longitudinal section through a track that shows elevation and depression.  Also, a drawing showing grade line of a railway, usually obtained from levels taken on top of the rail. 
(2) Cross sectional shape of the wheel tread.  In the UK there are a number of profiles, the P8 profile is most common on UK vehicles.  UoS


A collection of activities resulting in a change of state of the infrastructure including design, construction, installation, modification, maintenance, renewal and disposal activities.RT

Project Management Control System

The computer application which was by Railtrack for controlling time and cost elements of projects.  RT

Project Manager

Person responsible for managing all aspects of an infrastructure project as defined by the Project Manager’s remit in accordance with the specification and terms agreed with the supplier at contract award.RT

Project Release

A short term initiative to spread awareness of Railtrack standards.RT

Project Resolve

A long term initiative inaugurated in 1998 to classify, review and rationalise Railtrack standards.RT

Project Safety Case

A set of documents which specify how a project is to be safely designed, constructed, commissioned, operated, maintained and decommissioned.RT

Project Safety Strategy

A document that describes the safety policy and arrangements for a single project or group of similar projectsRT


Project expenditure.RT


A national performance improvement initiative, commencing 1998.RT


Moving a train using a locomotive at its rear.RT

Property Action Line

A formerRailtrack Property national telephone help desk for customers to report faults and provide feedback.  RT


In a specialised sense, used for the rules governing the protection given to a train which stops in an unusual location or becomes derailed, to stop another train hitting it.RT


A computer based system for train timing and pathing.  Train planners enter details of calling stations for a proposed train service and journey timings are produced as timetables in a variety of formats.  To be replaced by APLAN.RT


WCML infrastructure enhancements upto May 2002 to improve capacity, journey times and to secure additional revenue.RT


Additional WCML infrastructure enhancements upto 2005 to improve capacity, journey times and to secure additional revenue.RT


A computer system which extracts performance data from PALADIN, adds in data from FRAME and converts it to an excel spreadsheet.  For the PROMPT initiative. RT

Push Pull

A method of locomotivehauled train working in which the locomotive is permanently attached at one end of the train and when at the rear, is remotely controlled from a drivers cab built into the leading vehicle (see DVT).  Its advantage is that runround moves or turnover locomotives are unnecessary.RT


Q Link

The database run by Linkup which holds information relating to prequalification of suppliers to the railway industry.RT

Q Trains

just one tool in the rail industry’s campaign to stamp out trespass and vandalism.

Q Trains

Travel through trouble spots with the British Transport Police onboard.  If they see trespassers, the train stops so they can be apprehended.  Named after World War II warships that masqueraded as merchant ships.RT

Quadrant Analysis

A way of presenting information to highlight and explain trends.RT

Qualifying Expenditure

Expenditure recoverable from TOCs using major stations.RT


Radio Block Centre (RBC)

Nerve centre of any moving block system where the status of the infrastructure and the locations of all trains is known and where limits of movement authority can therefore be issued to all the trains within the control area.UoS

Radio Electronic Token Block (RETB)

Radio based block system where a coded message is sent to a particular train. This message is acknowledged in a secure manner to the signal box or control centre and allows the driver to move from a station onto a single track section of railway.  Particularly suited to low traffic routes.  May include ATP and radio controlled points.UoS

Radius of Curvature

A measure of the severity of a curve in a track layout based on the length of the radius of a circle that would be formed if the curve were continued.UoS


A rolled steel shape designed to be laid endtoend in two parallel lines on sleepers (US: ties), to form a track for railway rolling stock, travelling cranes and the like. There are two main types of rail in use in the UK.  Flatbottom rail is the most common, while Bullhead rail is still in use in sidings and on branch lines.  Network Rail has adopted UIC60 rail (which weighs 60 kg/m or 125 lb/yd) as its standard for high speed lines.  The previous standard, which is still being installed, is equivalent to the UIC 54 rail, and weighs about 113 lbs/yd or 54 kg/m

Rail Bond

A device used to transfer an electric circuit at a rail joint.UoS

Rail Creeping

intermittent longitudinal sliding movement of rails in track under traffic or because of temperature changes.  The effect of rail creeping is resisted by anticreepers or rail anchors.UoS


Records of broken and defective rails, meeting the requirements of Network Rail’s Group Standards organisation.RT

Rail Fastenings

(see Fastenings, track).UoS

Rail Foot

The flat bottomed part of the rail, held down by the fastenings.UoS

Rail Head

The top portion of the rail that the wheels run on.UoS

Rail Incident Officer

Normally a Network Rail employee who takes control at the scene of a rail incident or accident.RT

Rail Industry Safety

Strategy Committee a body set up in 1998 and composed of representatives of railway industry parties affected by changes to Railway Group Standards. Their remit is to provide advice concerning high level or strategic issues affecting Group Standards to Railway Safety and Standards Board when requested.RT

Rail Joint, Insulated

A rail joint which arrests the flow of electric current from rail to rail, as at the end of a track circuit, by means of nonconductors separating rail ends and other metal parts.UoS

Rail Regulator

An officer appointed by the Government to regulate the railway industry.RT

Rail Seat

Those areas on the upper face of a sleeper normally between 400mm and 660mm from each end where the rail or chair sits.RT

Rail Section

The pattern or dimensional details of rail, such as width of base, height of rail, thickness of web, width and thickness of head, angle of head, and angle of base. Each particular pattern is identified by a brand name or symbol such as ASCE, AREA, ARA, PRR, UIC and others in addition to its weight per yard.UoS

Rail Tensors

Hydraulic devices for extending CWR during rail stressing.RT

Rail Users Consultative Committees

Replaced the old Transport Users’ Consultative Committee.RT

Rail Web (UK)

See Web.UoS


(see Rail Data).UoS


A project to update and expand the transport of mail by train; involved Railtrack, Royal Mail and Rail Express System (RES).RT


The privately owned company (plc) that bought the railway infrastructure at the time of privatisation.  Railtrack was put into Railway Administration by the UK government in autumn 2001, partly as a result of the Hatfield railway accident.UoS

Railtrack Corporate Manual

The suite of documents that fully defined the standing orders for the governance of the whole of Railtrack as instructed by the Board of Railtrack plc.RT

Railtrack Energy Database

A bespoke computer system that operated on a Microsoft Access database.  Each Railtrack zone operated the system in the Finance department, and HQ Procurement operated a master system with the aggregate of data of all Zone and HQ departments.RT

Railtrack Financial Asset Records

System which was used by Railtrack to record the purchase cost and the current book value of assets.RT

Network Rail Crossing Risk Model

A software package designed to calculate risk levels at automatic level crossings.RT

Railtrack Line

That part of the Railtrack organisation that was the ultimate responsibility of the Chief Executive.RT

Railway Group

comprises Network Rail, the duty holders of railway safety cases accepted by Her Majesty’s Railway Inspectorate (HMRI), and the British Railways Board while it was owner of train operators.RT

Railway Group Standard

(see Group Standard).

Railway Safety Case

A set of documents submitted to and accepted by the Health and Safety Executive pursuant to the Railway (Safety Case) Regulations 2000, based on advice from HMRI, Railway Safety and Network Rail. RT+UoS

Railway Safety and Standards Board

Railway industry group owned notforprofit company in charge of setting Group Standards, auditing performance and pushing forward the safety agenda through research and development. UoS

Railway Skills Council

An organisation owned by all the members of the railway group charged with promoting quality education and training for all railway staff. RT+UoS

RAMS Reliability, Availability, Maintainability and Safety

An omnipresent set of terms when talking about safety and performance on railways.  See individual terms for details. UoS

Rapid Response Procedure

(1) the means of calling the contractor to incidents by Zone Duty Contracts Managers or Contractors Infrastructure Fault Control or (2) the means defined in Railway Group Standard GA/RT/6001 for quick implementation of amendment to a Group Standard.RT


combination of RCM(1) and RCM(2) to optimise infrastructure maintenance.  UoS

Reactionary Delay

The delay to trains resulting from an earlier train delay.RT

Reactive Maintenance

Maintenance performed in reaction to the results of an inspection or an alert by a user of an asset or by a third party.  Opposite of Preventative Maintenance.UoS


A dead end siding allowing trains to be shunted off the running lines; also a place of safety in tunnels and alongside high speed lines where employees can stand in safety.RT

Regenerative Braking

A form of dynamic braking using the traction motors as generators, the power produced is returned to the supply system.UoS

Registration Arm

Shaped Steel or aluminium arm used to position the contact wire of the OLE (OHLE) accurately with respect to the portals or other support structures of the catenary system.  Plastic or porcelain insulators are used to mount the registration arm from support structure. UoS


(1) signallers can regulate the train service by giving priority to one train over another, (2) In maintenance terms this means levelling the ballast (see also "Tamping").RT

Regulated Income

income regulated by the Office of the Railway Regulator (ORR).  Regulated Income is also described as franchised income.RT

Regulation (1)

The order in which trains are run in practice so as to minimise delay (2) statutory statement.RT

Relative Braking Distance

The provision of a relative braking distance between trains is based on the assumption that the train in front cannot stop instantaneously and that the train behind can therefore follow with a very small gap.  Essentially based on the reaction time to start braking when the train in front is starting to decelerate.  The railway industry has never accepted this as a viable proposition because there have been instances where trains stopped dead, e.g., as the result of a collision with another train.UoS


An electromechanical switching device used in many types of signalling systems; it "relays" instructions to signals and points.  The device contains motors or magnets, which, when energised, cause electrical circuits to open and / or close Relays are now being superseded by Solid State Interlocking (SSI), in particular in areas controlled by IECC signal boxes.RT+UoS


To replace worn out or damaged track.RT


A measure for the probability that a piece of equipment is working normally or for the ratio between the time during which a piece of equipment is functioning correctly and the total period during which it is needed.UoS

Reliability Centred Maintenance (RCM1)

an approach to maintaining fixed and movable assets with the objective of achieving a target reliability by tuning both periodicity and scope of maintenance activities in line with the demands placed on the particular piece of equipment by its operational role.UoS

Relief Line

A Great Western term for the slower line in a multiple track area usually known as the Slow Line elsewhere.RT

Reminder Appliance

A device of control used to remind a Signalman that a particular lever, button or switch must not be operated in the normal manner (eg.  a lever collar.)RT


A document that defines the scope of the project, the authority of the project manager, the deliverables and any other relevant information.RT

Remote Condition Monitoring (RCM2)

describes the use of telemetry and complex algorithms to assess the state of railway infrastructure remotely, with the objective of managing maintenance effort so that assets cannot deteriorate beyond the point where they would affect safety and reliability.UoS


includes: information, funding, personnel, plant and equipment, time.RT


A braking device, usually poweroperated, built into a railway track to reduce the speed of vehicles by means of brake shoes which, when set in position, press against the sides of the wheel flanges.UoS

RETB Radio Electronic Token Block

A system for signalling trains on single lines by a combination of computer control and radio messages.  There is no physical token but the software issues messages allowing trains to proceed on the single line.  RT

Return On Capital Employed

This is a ratio used to assess the return that the company is producing for the shareholders.  It is expressed as the profit made in a year as a percentage of the assets.RT

REV (rev)

found on international registered wagons to denote date of overhaul.RT

Revenue Project

Non routine activities that do not result in a capital asset yet still deliver a measurable output.  Revenue projects are funded through the profit and loss account and may be either technical support, research & development, standards development etc.RT

Rheostatic Braking

A form of dynamic braking using the traction motors as generators, the power produced is dissipated in resistors.  This is the only form of dynamic braking that can be used with autonomous traction.UoS

Ribbon Rail (US)

continuously welded rail free of joints or with very few joints over long stretches.UoS

Right of Way

land or water rights used for the railways roadbed and its Structures and kept clear for operations.UoS

Right Side Failure

Something which fails but does not fail to an unsafe condition, e.g., a green light going to red.  (See also the opposite Wrongside Failure)RT


The combination of the severity of a hazard and the likelihood of its occurrence.RT

Risk Log

A continually updated record of identified hazards together with their associated level of risk and control measures necessary.RT


Railway jargon for railway line.RT

Road Railer

Road trailer which can be converted to rail operation by adding a rail bogie between two trailers.UoS

Road Rail Vehicle

A vehicle capable of running on both road and rail.  Normally used to travel by road to the nearest point for accessing a work site by rail.  May have a builtin turntable to change direction.UoS

Rod, Operating

A rod attached to a point blade, derailment device or other moving component, moving it from one position to another.UoS

Rolling Contact Fatigue (RCF)

The process whereby the high forces in the contact patch cause the development of cracks that penetrate into the rail head or into the tread surface.  The cracks can grow just underneath the surface, causing flaking and spalling or they can ‘turn down’ and lead to rail breaks or severe railhead and wheel damage.UoS

Rolling Stock Pages

Passenger and freight vehicles, locomotives, multiple units, any vehicle in revenue service.RT

Rolling Stock Pages Acceptance Board

The Network Rail sponsored organisation responsible for the management of the T&RS route acceptance process with responsibility for the approval of route acceptance requests and the issue of T&RS Certificates of Authority to operate (CoA) and Certificates of Technical Acceptance.RT

Route Acceptance Request

Application by an operator, owner, etc.  to run a new or modified vehicle on Network Rail’s network.RT

Route Availability

A code used to indicate which rolling stock can use which routes.  Must be used in conjunction with the loading gauge availability.RT The allowable mass per axle, commonly referred to as the axle load, is a further important constraint.  In most cases though, this last constraint can be overcome by reducing the payload when using a particularly restrictive route.  In Britain, the maximum allowable axle load is now generally 25.5t and the axle load capability of railway routes is classified in terms of Route Availability (RA) with the following main ranges:

  • RA 16 up to 20.3 tonnes per axle;
  • RA 79 up to 24.1 tonnes per axle;
  • RA 10 up to 25.4 tonnes per axle.UoS
Route Crime The current term for what was previously know as Trespass and Vandalism.  It includes suicides and other illegal acts on railway land.RT+UoS


The original main type of maintenance contract between Railtrack and the IMUs (see also IMC).RT


The Railtrack contract for rapid response to structure damage and flooding.RT


Network Rail Group Standard for the UIC60 based rail system, including associated switch & crossing work (S&C).  Features are: design for 30 tonne axle load, suitable for 140mph tilting trains, reduced impact forces, improved ride quality, inclined rails through S&C, optimisation of design for mixed traffic.UoS


The Railtrack companywide information systems service organisation which, in June 1995, brought into one team the company’s full time Information Services people.RT

Rule Book

A book which incorporates most of the rules to be observed by general railway staff for the safe operation of the network.  This book is now published in 14 volumes, each one "personalised" by job type, e.g., No.3 Signalman, No.4 Train Driver etc.RT+UoS

Rules of the Plan

Rules which are applied to bids from train operators for scheduling train paths on Network Rail’s network.RT

Rules of the Route

An agreement between Network Rail and train operators which states when lines can be temporarily closed, or speed restricted for maintenance and renewal work.RT

Running Rail

The rail or surface on which the wheel bears, as distinguished from a check rail, guard rail or wing rail.UoS

Running Round

Transferring a locomotive from one end of a train to the other by means of a loop.RT


S&C Layout

A crossover, turnout, double junction, etc made up of a number of subassemblies complete with all bearers and other components except point motors.RT

S&C Unit

Half or full set of switches, a crossing, check rail, expansion switch, cast crossing or other subassembly machined or shaped for a use as part of S&C.RT


The line between Milford, Ferrybridge and Swinton, so called because it was built by the Swinton & Knottingley Joint Railway.RT

Safety Advisory Panel

The body responsible for type approval and for providing recommendations when requested by train operators and train builders.  RT

Safety Authority

The person or persons accountable for safety.RT

Safety Case

A formal presentation of evidence, arguments and assumptions aimed at providing assurance that the design and implementation of a system complies with the safety objectives.RT

Safety Critical Defect

A defect which, on assessment, is an immediate threat to the safety of trains or the public or Network Rail staff and warrants trains being stopped or cautioned until remedial action is undertaken.RT

Safety Critical Work

Defined in the Railway (Safety Critical Work) Regulations, 1994 as maintenance, repair, renewal or alteration of:

  • permanent way or other means of guiding or supporting vehicles
  • signals or other means of controlling the movement of vehicles
  • any means of supply of electricity to vehicles or to the means of supporting vehicles which could affect the health and safety of personnel on a transport system RT

Safety Management System

A proven system which, when followed, enables a company to perform tasks safely, at all levels of the organisation.  The system to achieve this blends personnel, resources, policies and procedures together.  Such a system must also recognise instances when it is inadequate to requirements and generates change to the system to correct the deficiencies.RT

Safety Review Group

The Zone management group responsible for approving any change (except T&RS change) that has a potential impact on safety.RT

Safety Risk Assessment

A risk study for a specific safety issue identified within the risk log.RT

Safety Validation Document

Documentation prepared in support of safety validation of an organisational or SMS change, including relevant sections of the Network Rail Railway Safety Case, safety policy statements and safety arrangements.RT


A method for assisting adhesion between driving wheel and rail.  The sand is carried on board the vehicle in a sandbox and is ejected, normally under air pressure, onto rails immediately in front of the driving or braking wheels to assist adhesion.  It is usually operated by a push button in the driving cab or automatically by wheelslip equipment. UoS


A mixture of sand and antifreeze, used for assisting traction adhesion during extreme weather.  Sandite S4 also contains steel shot to assist track circuit operation.RT

SBI Gauge

loading gauge in Britain which permits operation of roadrail swap body vehicles.RT

Schedule 3

Part of a contract or Track Access agreement, between a Freight Operating Company and Network Rail, defining the basic conditions of operation.RT

Schedule 8

The section of a Track Access Contract governing performance payments.RT


A lump of wood either placed in an open switch of points to prevent movement, or on a rail under a wheel to prevent a vehicle from being moved.RT

Section Signal

(often called the "starter") the stop signal which controls the entrance to the Block Section (or intermediate block section) ahead.RT

Security Incident Tracking System

log and reporting tool for security incidents affecting information systems.RT

Security Rules

Used to prevent business units from accessing other business units’ data.RT

Semaphore Signals

Such signals are usually worked mechanically by wire from a signal box lever frame, but can be electrically operated.  They use mechanical arms rather than coloured lights to display aspects.  Traditional types are "upper quadrant and lower quadrant" position where the "clear" positions are at approximately 45o to the horizontal.RT+UoS

Sequential Locking

A refinement of "Route Interlocking" which ensures that signals are operated only if particular processes occur in a certain order (e.g., occupying & clearing of the overlap track circuit).RT+UoS

Service Life

(1) the period of effective functional activity of equipment or (2) the equivalent millions of gross tonnes of rail traffic that a track component is expected to carry from new before requiring renewal.RT


A complete train, including loco and carriages or a multiple unit train.RT


An opening between a tunnel and ground level above, usually provided to ventilate, to relieve aerodynamic pressure from trains or to give access during construction or afterwards.RT


A word used in procedural documents to express a mandatory requirement.  Compare with should, must, will, may.RT

Shared Services

A team set up to provide an all encompassing support structure, to ensure that the Business Management Information System (BMIS) is available to be used as and when required.RT


One of the consequences of rolling contact fatigue, resulting from the propagation of cracks underneath and parallel to the surface of the rail head or running surface of the wheel.  The phenomenon is more pronounced on rails where the traffic is predominantly in one direction. Railhead damage takes the form of pieces of the rail or tread surface becoming detached or being torn off.  The severity of the damage caused by shelling is somewhere between that associated with flaking and spalling.  However, this is largely a qualitative differentiation.  UoS


Term used as a shortened version of "collector shoe" to denote a third rail current collection device mounted on the bogie of a direct current electric train.  Shoes are normally distributed along the train and connected by a power train line cable to avoid loss of power at gaps in the current rail (see also:Conductor Rail and Gapping.  Different types of shoes are required for top, side and underrunning.UoS

Shop Made Joint

An insulated rail joint prepared and assembled in controlled workshop conditions, i.e.  not outside or on site.RT

Short Term Planning

One off bids for train paths.  (see also Sport Bids)RT


A word used in procedural documents to express a recommendation or advice.  Compare with shall, must, will, may.RT

Shoulder Peak Services

Train service timetable immediately before or after the peak period.RT

Shoulder, Ballast

The portion of ballast between the end of the tie and the toe of the ballast slope.  It distributes the traffic load over a greater width of roadway and helps hold the track in alignment.UoS

Shunting Signal

A signal which is provided for shunting purposes only.RT


In railway terminology, a shuttle usually means a service operating back and forth between two stations without an intermediate stop.  The Channel Tunnel service is called Le Shuttle and many cities operate shuttle services between airports and city centres.  The Gatwick Express, which operates in the UK between Gatwick Airport and London (Victoria) is one such.  Sometimes also erroneously used to refer to short distance, regular interval services with intermediate stops.UoS

Side Track (C.T.)

A track used to temporarily store cars.  (UK: carriage line)UoS

Side Wear

The reduction in rail head width due to wear caused by wheel flanges coming into contact with the rails as trains run on curved track.  Flange contact is prevented by maintaining good wheel and rail profiles and by keeping to the speed range for which the track is canted.RT

Siding (US)

A track auxiliary to a main or secondary track for the meeting or passing of trains.  (UK: Centre Siding, a Reversing Siding).UoS

Signal and Telegraph

An obsolete term still commonly used to refer to the people and the companies who maintain signalling equipment.RT

(Signal) 'Box (UK)

Railway term for a signal box or signal cabin.  In mechanical signal boxes there is generally a first floor with the mechanical levers and the block instrument while the space underneath is taken up by the interlocking mechanism and associated relays.  (US: Tower).UoS

Signal, Highway, Electric (US)

A highway crossing signal which is actuated automatically by the approach of a train and which then displays one or any combination of several features such as red lights (flashing or nonflashing) horizontally swinging disk, crossing gates, or warning bell.  All are designed to warn motorists of the approach of a train.UoS


UK term for person employed to operate or supervise the control of signals.  Traditionally accommodated in a signal box, more recently a control room, where the signalling levers or controls are located. Formerly identified as "Signalman".UoS

Signalling, Automatic Block

A system of signals of fixed location, each located at the entrance to a block, to govern trains and engines entering and using that block.  Such signals govern movements over a series of consecutive blocks. They are actuated by a train or engine or by other conditions affecting the use of the block, such as a broken rail, switch not properly lined, car standing on a turnout foul of a main track or other track obstruction.UoS

Signalling Equipment Technical Agent

The organisation responsible for supporting and managing the product qualification and configuration control process on behalf of the asset owner.RT

Signalling Incident System

(wrongside fault reporting) – records and forwards details of the more serious wrongside faults to infrastructure maintenance engineers, to allow for prompt analysis of the event.RT

Signalling Restructuring Initiative

Achieved after the 1994 strikes.  Inter alia, allows signallers to operate computer equipment not directly part of their signalling duties, and thus to operate Electronic Train Reporting (ETR).RT+UoS

Signalman (UK)

Politically incorrect term for "signaller".  Not to be confused with the same term used in the US for a signal maintenance person or signal maintainer.UoS

Signal Monitoring and Reporting of Trains system

– provides information automatically on actual train running.RT

Signal Passed at Danger (SPAD)

Situation where a train driver fails to bring the train to a complete stop at a red signal.  In 1999 there were over 800 SPADS on Railtrack lines. Most are only by a few metres, caused by variable adhesion or poor driver control.  They usually cause no collision thanks to the provision of the overlap after the signal. UoS

Signals Passed At Danger Management Information System

– supplied to safety management across the industry and the basis of reports to the Health & Safety Executive.RT

Silverlink Train Services

Trading name adopted by North London Railways in 1997.  "Silverlink Metro" is used for the EustonWatford and North London Line services, and " Silverlink County" for the EustonNorthamptonBirmingham trains.RT

Simplified BiDirectional Signalling

Signalling provided to allow trains to run in the "wrong" direction during engineering work, line blockages, etc without resorting to pilotmen.RT

Simplified Direct Reporting

Manual reporting of train times to TRUST using a computer terminal and standard TRUST screens.  This includes signalbox terminals formerly known as ETR.RT

Site Instruction

An instruction by the employer to the contractor relating to an activity which is included in the terms of the contract and which does not vary the contract.RT

Six Foot (UK)

The space between adjacent running lines of a two track railway.  Where there are more than two tracks, the distance between pairs of lines is usually greater than six feet.UoS

Six Foot

Space between two sets of tracks (which may be more than six foot.) (Also see Ten Foot and Interval.)t

Sixty Foot

60ft is the standard length of single rail.RT

Slab Track

A form of railway track comprising a concrete base to which the base plates carrying the rails are secured.  It eliminates the need for individual "sleepers" (q.v.).UoS


Wood, concrete or steel object which holds the rails apart and supports the track on the ballast.RT

Sleeper (UK)

in the US known as "ties", short for "crossties".  The transverse members of trackwork, made of wood, concrete or steel, or even plastic composite, which are used to secure the rails at the correct gauge.  Cast steel chairs fixed to the sleepers hold the rails in place by means of clips or keys.  UoS

Slide fence

A warning device connected to signals which warn trains of rock or landslides when fence wire is broken by rock fall.UoS

Société Nationale des Chemins de Fer Français

French national railways. RT

Solid State Interlocking (SSI)

Any interlocking using electronic components and software to carry out the safety critical interlocking actions.  Often refers to standard UK system.UoS

Solid State Interlocking

A processor based system for controlling the interlocking between points and signals, as well as communication with lineside signalling functions.  SSI is based on a central interlocking unit which has serial communication with trackside functioned modules (TFMs) which control signals and points.  RT+UoS

Sound Exposure Level

The level of sound accumulated over a given time interval or event.  Technically, the sound exposure level is the level of the timeintegrated mean square Aweighted sound for a stated time interval or event, with a reference time of one second.  Also written as SEL.UoS

SPAD Investigator

A person identified by the Zonal Safety and Standards Manager as having the necessary skills required for investigating the cause(s) of a signal passed at danger.RT


One of the consequences of rolling contact fatigue, resulting from the propagation of cracks underneath and parallel to the surface of the rail head or running surface of the wheel.  The phenomenon is more pronounced on rails where the traffic is predominantly in one direction. Railhead damage takes the form of pieces of the rail or tread surface becoming detached or being torn off.  The severity of the damage caused by spalling is generally felt to be greater than that associated with shelling.  However, this is largely a qualitative differentiation.  UoS


Early removal or non imposition of a temporary speed restriction.  RT

Special Conditions of Contract

Documents which amend a specific set of industry standard conditions.  They also include supplementary clauses covering issues specific to the railway environment or reflecting corporate policy.RT

Special Track Work

Switches, points, crossovers or other line intersections.UoS


A contract document setting out mandatory requirements.RT


The Network Rail person or persons or organisation appointed to produce a contract specification or technical workscope associated with any individual contract.RT

Spiked Switch US)

A turnout with one or both switch rails held in fixed positions by spikes (or clips and clamp), usually to prevent a disconnected or damaged switch from being thrown through error, or to prevent trains from using a track that has been taken out of service.  see clipped switch (UK).UoS

Splice Bar

A joint bar.  (UK: Fishplate)UoS


The Network Rail person having responsibilities for progressing all aspects of the scheme in accordance with Network Rail Investment Regulations, etc and who will also normally represent the client.RT

Spot Bids

bids for train paths for inclusion in the permanent timetable after it has been published; spot bids have no contractual right to get into the GBPRT.  (see also STP – Short Term Planning)RT


Designation of rail surface damage caused by powered wheels slipping on the rail and causing localised heating of the railhead.  UoS


Parking of trains which are not in use for a period (e.g., overnight).RT


in Overhead Line Equipment, the lateral deviation of the contact wire from the centre line of the track. The wire is staggered from side to side of this line, within fixed limits, to even out wear on the pantographs of trains.RT


(1) document established by consensus and approved by a recognised body that provides, for common and repeated use, rules, guidelines or characteristics for activities or their results, aimed at achieving the optimum degree of order in a given context; or (2) Railway Group Standard or Network Rail Line Standard.  RT

Standard Infrastructure Performance System

civil engineering equivalent of PEARS.RT

Standard Risk Activities

Those activities assessed by risk assessment not to be high priority risks, based on the likelihood/consequence risk matrix.  These works, may be regularly occurring works which can be assessed by generic method statements for the varying processes rather than by writing a detailed site specific method statements. RT

Standards Management Group

A forum that was envisaged by C Change for review of changes to Railtrack standards but which was replaced in 1998 by alternative processes.RT

Standards Portfolio

The complete suite of published Network Rail standards.RT

Standards Review Manager

A manager within the Network Rail Line Safety Directorate responsible for ensuring that the portfolio of Network Rail Line Standards is managed according to the due process.RT

Station Limits

The portion of line between the Home Signal and the Section Signal for the same line worked from the same signalbox.  (NB: this term applies irrespective of whether or not there is a station open for passenger or freight use.  It does not apply on a Track Circuit Block line.RT

Statistical Journal Entry

A journal entry in which nonfinancial information is entered, such as headcount, production units and sales units.RT


freight access charging system, generating rates for freight services.RT

Stewardship Report

A report prepared by the RT1A contractor to comply with the Railtrack Line Specification on Stewardship Reports providing an overview of the safety issues relating to the works on each contract including infrastructure performance.  Each report covers a specified threemonth period.RT

Stock rail

The fixed rail on each side of the points, against which the switch rail rests.  On standard points, one stock rail is straight and the other curved to carry trains on deviation.UoS

Stock rail bend

The bend or set which must be given the stock rail at the vertex of a switch to allow it to follow the gage line on the turnout.  Usually, only one stock rail of a switch is bent.  The opposite one is straight.UoS

Stop Block

A buffer stop.RT

Stop Signal

Any main signal which can display a stop aspect or indication.RT

Stop, Car (US)

A device for stopping a car by engaging the wheels, as distinguished from a buffer, which engages the coupler of a car or the front buffer beam of a locomotive.UoS

Strategic Materials

Restricted availability components with a potentially critical impact on operating performance and which must be freely transferable between contractors, and as defined in the Strategic Materials Catalogue.RT

Strategic Rail Authority

A body proposed by the Parliamentary Select Committee for Transport report in March 1998 and implemented as the Shadow SRA in 1999.  Became a legal authority at the beginning of 2001.UoS

Stress Restoration

The process of stretching CWR so that the SFT of the rails is the same as it was before the CWR was disturbed for maintenance and other purposes.RT

Stress Transition Length

The length of track at each end of a length of CWR between the point of zero stress (the adjustment switch) and the point of full stress (i.e.  stress free at 27ºC).  Note: a stress transition length may be used as an anchor for stressing purposes but must not contain any S&C even if these are strengthened for use in CWR.RT

StressFree Temperature

The rail temperature at which the rail is the same length as it would be in an unrestrained state and at which, therefore, there is no thermal extension or compression force present.  Generally used when discussing continuously welded rail (CWR).RT+UoS


The process of stretching CWR so that the stressfree temperature of the rails is within the required range (21 to 27ºC).RT

Stressing Naturally

The clipping down of the rail without tensors (stretching equipment) being used, when the rail temperature is between 21 and 27ºC.RT

Stretcher Bar

Metal bar that connects the two switch blades in a turnout in one or more places and allowing adjustment of the relative position of the switch rails.UoS

Strike in Point

The position on the approach to an automatic level crossing at which a train initiates the operating (closing) sequence.RT

String lining (US)

A method for determining the corrections to be made in the alignment of a curve, by measuring ordinates to the outer rail and without the use of surveying instruments.UoS


A construction such as a bridge (rail, road, foot or equestrian), viaduct, retaining wall, tunnel or similar, signal or electrification post or gantry, station construction such as a platform wall, track drainage manhole or cable pit, and any other construction on Network Rail controlled infrastructure.RT


Track section with access from only one end.UoS

Stub End

A section of conductor rail fed from one point only.RT


Any material of superior character, which can be spread on the finished subgrade of the roadbed, to provide better drainage, prevent upheaval by frost and better distribute the load over the roadbed.UoS


The prepared surface of the natural ground or upper surface of fill material.RT

Subsidiary Signal

A miniature semaphore arm positioned under a main semaphore arm, or a position light aspect positioned below a main aspect, which when cleared, authorises a Driver to pass the main arm or aspect at Danger and to proceed cautiously.RT


A location where power is received at high voltage and changed to required voltages and characteristics for distribution to the catenary system, third rail, and other electric apparatus.  It may contain transformers, rotating machinery, circuit breakers, sectionalising switches, rectifiers, etc.UoS


The track substructure includes the formation, ballast and any geotextile, geogrid, blanket.RT


The height the outer rail is raised above the inner or grade rail, on curves, to reduce the lateral acceleration of moving trains.  This should not be confused with crosslevel, on tangent (straight) track.  (UK: Cant)UoS

Supervisory Control and Data Acquisition System (SCADA)

centralised control of routine and emergency operation of a large technical system using data links to remote components and databases for managing and monitoring their performance.UoS

Supervisory Control Centre (SCC)

Traffic control centre for a railway using modern forms of train control (US term).UoS


A module within PROCSYS for recording supplier performance information.RT


A generic term used to describe a company, contractor, consultant or partnership supplying works, goods or services.RT

Supplier Qualification

A process whereby all potential suppliers or contractors are subject to scrutiny on a range of topics to ensure that each supplier or contractor is appropriately qualified to be invited to tender for a Network Rail contract.RT

Surface Water Drain

A drain designed to collect water from the surface and/or from the surrounding ground continuously along its length.RT

Surface, running (tread)

The top surface of the railhead on which the wheel tread rides or runs.UoS

Surfacing, out of face

Raising the entire track to a new grade.UoS


An organisation primarily concerned with the creation of cycle paths throughout the UK.  Their name is a contraction of sustainable transport.RT

Swap Body

A system for conveying road freight vehicle bodies on rail vehicles without throadrunning gear.RT

Swing Nose Crossing

A point in which the flangeway at the nose is arranged to open or close according to which way the points are set so as to provide a smooth passage for the train wheels.RT

Switch (US)

A track structure used to allow rolling stock to move from one track to another.  A pair of movable point blades, together with their fastenings and operating rods, provides a connection with variable geometry (2 pcs).  See also turnout.  UoS

Switches and Crossings (S&C)

The specially designed rail components allowing trains to change tracks.  Any track elements which are not plain line. UoS

Switch Fixtures

The connecting and bearing parts for the rails of a split switch.UoS

Switch Guard

A structure, usually of manganese steel, secured outside the running rail at the point of switch, with suitable flares to engage with the tread rim of wheels and guide them past the switch point without blow or undue wear.UoS

Switch Heel

blunt end of a switchblade that is connected to the closure rail.UoS

Switch Heater

A device for melting snow with heat generated by an electric current, or by gas or oil; used for movable parts of switches, etc.UoS

Switch Lock

Mechanical device attached to both the switch rail and stock rail to ensure that the switch rail remains fixed for the passage of a train.  In many countries, they are a legal requirement where passenger trains are operated.  The turnout is also electrically locked by the control system (interlocking) and by track circuits occupied by a train passing over them (see also Detection).  UoS

Switch Lock

A fastener, usually a spring padlock, used to secure the switch or derail stand in place and thus to maintain the correct position of these components.  A switch lock is used in situations where a switch rail or derail is only operated rarely.UoS

Switch Plate

A special metal tie plate for use on switch ties, each plate being long enough to extend not only under the stock rail and its supporting braces, but also under the switch rail in open position.  Switch plates are furnished in sets to correspond with switch length.  There are two plates to each tie; however, at point of switch, the two may be replaced by a gage plate which carries both switch rails.UoS

Switch Rail

The moving portion of rail on each side of a set of points.  Also known as Point Blades. RT&UoS

Switch Rod, adjustable

A switch rod with an attachment for altering its length to keep the switch rails in their proper positions.  Adjustment is usually effected through staggering holes in the clips which connect switch rod and switch rail.UoS

Switch, Staggered point

A switch in which the toe of one switch rail is placed in advance of the other, as in a turnout from inside a curve.UoS

Switch Target

A visual day signal fixed on the spindle of a switch stand, or the circular flaring collar fitted around the switchlamp lens, and painted a distinctive colour to indicate the position of the switch.UoS

Switch, Throw of

The distance, measured along the centre line of the rod nearest the point connecting the two switch rails, through which switch points are moved sidewise to bring either point against the stock rail; standardised at 43/4 inches.UoS

Switching Yard (US

) (see Marshalling Yard (UK)).UoS

Switch Toe

The pointed end of a switchblade that rests against the stock rail.UoS

System Review Panel

Specialist body with responsibility to consider specific system and safety issues.RT

Systems Management Framework Design

An RTIS project to identify, document and implement IT processes, initially in the Operations and Technical Services area. R


T2 X, D, H, T (Blockage)

Arranging protection on line when Tiii Possession is not required (see Tiii Possession.RT

Tache Ovale

A rail fault consisting of a void within the rail, with nothing visible on the surface of the rail. It can be detected with ultrasonic scanning equipment.RT

Tail Lamp

A lamp carried on the rear of every train (it may be built into the vehicle) to indicate that the train has arrived complete and no vehicles have become detached. If a signaller sees a train pass without a lit tail lamp he must stop the train.RT


Process that pushes ballast under sleepers (see also Regulate) to fill voids so as to maintain the correct geometry of the track.  Can damage the ballast and may not be effective due to "ballast memory", that is the tendency for ballast to return to the mutual positions existing before tamping (see stone blowing).UoS

Tangent Track

Track without curvature.UoS


Time and Relative Dimensions In Space. Even more improbably, it can stand for Ancillary Retrospective Data Information Service.  (see also TOPS)RT

Target 90

An initiative aimed at ensuring that 90% of WCML passenger trains arrive at their destination within ten minutes of their scheduled arrival time.RT

Task Specification Form

A document defining scope and criteria to be adopted, particularly with respect to PMCS software changes.RT

Team track

A track on which freight is transferred directly between railway cars and highway vehicles.UoS

Technical Approval

Technical approval signifies that, based on a systematic review, a professionally competent person or body is satisfied that:

  • the requirements of the remit have been established and met;
  • the appropriate standards and/or design criteria are proposed for the design/checking phaseRT
  • competent persons have used reasonable professional care in designing and executing the scheme;
  • the safety of railway operations and safe interworking have not been compromisedRT

Technical Contractor

A consultant, contractor or supplier engaged (by Network Rail) to supply a technical service.RT

Technical Review Group

An ad hoc temporary panel established under remit to consider specified technical issues.RT

Technical Support

Staff charged with the investigation into existing technologies and working practices (of Network Rail) to resolve technical issues arising.RT+UoS

Technical Support Group

Network Rail HQ Civil Engineering Technical Support Group.RT

Technical Workscope

The section of a contract document which, includes all projectspecific information and details the technical specification, implementation standards and assurance requirements.RT

Tell Tales

Marks made on each rail in a line with a suitable reference mark on an adjacent unclipped sleeper, in order to monitor the effectiveness of the anchor length.  A tell tale is required at each end of each anchor length.  That adjoining the free rail is the inner tell tale (which must be unclipped); the other is the outer tell tale (which must remain clipped).RT

Ten Foot (UK)

10ft is the central space between adjacent pairs of running lines on a four track railway.  Beware, this may actually be less than the six foot. UoS+RT


An assemblage of facilities provided by a railway at a terminus or at an intermediate point for the handling of passengers or freight and the receiving, classifying, assembling and dispatching of trains.UoS

Tesco Technical Services Company

, provides engineering services associated with traction and rolling stock maintenance.RT


High integrity mobile communications system developed specifically or emergency services and police use, originally intended for railway use.UoS

Thameslink 2000

The project by which the existing crossLondon Thameslink route is modernised.RT


The cylindrical pieces of an insulating joint which surround portions of the bolts.UoS

Third Rail

An additional rail beside the two running rails which carries electric current for trains which operate on this electrical system.RT

Third Rail System

Traction current supply system which uses an additional rail to transmit the electrical supply from where it is collected by collector shoesattached to the train.  See fourth rail system and conductor railUoS Through Ticketing The ability, in one transaction, to purchase a ticket for a journey using the services of more than one operator.RT

Tie (US)

A transverse support to which rails are fastened to keep them in line, gage and grade.  Usually wooden or concrete.  See Cross tie.  (UK: Sleeper)UoS

Tiii Possession

When an engineer takes absolute possession of a section of track or line.RT&UoS

Tie Plate (US)

A metal plate at least 6 inches wide and long enough to provide a safe bearing area on the tie, with a shoulder to restrain outward movement of the rail.  (UK: base plate or chair)UoS

Tie Plate, canted (US)

A tie plate tapered in thickness, usually on a slope of 1 in 20, for the purpose of inclining the rail toward the centre of track for easier maintenance of gage, more uniform wear of head, and central loading of rail.UoS

Tie Plate, twin (US

) a tie plate in two parts which mate to form a combined width equal to that of the stand tie plate, for use back of the heel of switch to the point where standard tie plates may be applied without their ends infringing.UoS


balks of wood supporting switches and crossings; can extend to two or more lines and be up to 20ft in length.RT

Time Division Multiplex

An electronic data transmission system that has two distinct railway applications – in power signalling installations and in remote control of a locomotive for pushpull working.RT

Time Table Data Base

A Journey Planner facility which allows the public to view timetable information remotely through the internet or VDUs at stations.RT

Token (or tablet)

A device carried by a Driver as his authority to run over a single line worked by the Electric Token Block System.RT

Top And Tail Working

Running trains with an engine at each end, usually during disrupted working to avoid timeconsuming runninground movements.RT

Top Ballast

Any material of a superior character spread over a subballast to support the track structure, distribute the load to the subballast, and provide a good initial drainage.UoS

TOPS Total Operations Processing System

, a prime source of train movement information for other systems. TOPS.  RT

Total Operations Processing System (TOPS)

computer based system used to record information from train describers, signal boxes, and track circuits at junctions.  TOPS provides a comprehensive system for monitoring a train’s complete movement cycle from workshop and maintenance through to service, safety restrictions, train schedules and performance.  Is used to monitor railway operations and rolling stock usage and for the management of maintenance.  Now described as TRUST.UoS


An assembly of rail, fastenings and sleepers over which railway carriages, wagons, locomotives and trains are moved.  The track is usually defined as the area covered by the rails, rail fastenings and sleeper hardware and the roadbed.  UoS

Track Access Notice

The means of publishing short term additions and alterations to the train plan.R

Track, Body (US)

Each of the parallel tracks of a yard, on which cars are switched or stored.UoS

Track Circuit

Means by which the passage of trains is detected and the information used to control signals provided for train safety and control.  This method of train detection (train location) uses a voltage which is applied at one end of a track section and detected at the other end.  An electric current must flow in the rails of the track which therefore requires insulation of the rails with respect to each other.  Rail joints between track circuit sections must be specially bonded at rail joints used by the signalling system.  When a vehicle enters the track circuit section the detection occurs when its wheelsets(wheels and axles) shortcircuit the rails and interrupt the flow of electricity to the receiver.  Track circuits can be based on High voltage, Pulse, DC, Audio Frequency signals etc.  The simplest track circuit consists of a relay energised by a low voltage circuit fed through the running rails of a section of track.UoS

Track Circuit Actuator

A device fitted to some vehicles, notably lightweight discbraked diesel railcars, which cannot be relied upon to activate track circuits when leaf mush is on the line or the rails are rusty.  It does not work if the lead mush is dry.RT

Track Circuit Activator (TCA)

Equipment provided on certain lightweight trains to improve their operation of track circuits.RT

Track Circuit Actuator Interference Detector

A lineside device which detects the radio waves caused by a Track Circuit Actuator on a passing train, thus giving an indication of the train’s presence even if the actuator fails to operate the Track Circuit.  It does not fail safe however.RT

Track Circuit Block

A modification of the Absolute Block System, employing track circuiting throughout.  As soon as the line is clear, a train may proceed to the next stop signal plus the required overlap beyond that signal. RT

Track Circuit Operating Devices

A special device which can be placed on a TCB line to provide protection, by operating TCB (Track Circuit Block).RT

Track Crossing

A cast or fabricated crossing assembly, used where one track crosses another at grade, and consisting of four connected crossings.UoS

Track Fastenings

The term commonly applied to baseplates, rail clips, screws and spikes.UoS

Track Fastenings

Auxiliary the term commonly applied to spring washers, tie plates, rail braces, anticreepers and gauge rods.UoS

Track Identifier

A rail fault consisting of a void within the rail, with nothing visible on the exterior.  It can be detected with ultrasonic scanning equipment.RT

Track Irregularity

Civil Engineer’s track identifier: generally a subset of Engineer’s Line Reference (ELR).RT

Track Level

A board with a spirit level attached, to level the rails of a track usually equipped with a series of steps to set superelevation on the outside rail of curves.UoS

Track Quality

An integral part of railway track recording systems.  Mounted on a track recording vehicle, it gives a comprehensive assessment of the condition of the track over which it runs.  The quality of the track is monitored to Railway Safety and Standards Board Group Standards’ requirements.RT+UoS

Track, Repair or Rip (US)

One of the body tracks in a car repair yard or shed, on which repairs are made to rolling stock.UoS

Track Sectioning Cabin

A building containing electrical switchgear and equipment which is arranged to connect together a number of sections of OLE.RT

Track, Spur (US)

A track connected with the parent track at one end only.UoS

Track, Storage (US)

One of the body tracks in a storage yard, or a track used for storage purposes.UoS

TrackLaying machine

A machine designed to minimise the manual labour of placing rails, fastenings, ties and other materials.UoS

Trackside Functional Module (TFM)

failsafe electronic unit of the SSI system which is able to control a multiple aspect signal or points and which transmits its status to the SSI central processor in the control room.UoS


Railway track or permanent way including buffer stops and level crossings in the immediate vicinity of the tracks.  The term includes longitudinal pit timbers but excludes the pits themselves.RT

Traction Current

Term used for electric power supply used on electric railways for trains.  Normally supplied by overhead wire or third rail and collected by a pantograph on the roof of the train in the former case or by shoes attached to the bogies in the latter.UoS

Traction Motor

Electric motor used to provide the driving or braking torque to a locomotive or multiple unit axle.  Used in dieselelectric and electric systems.  The traction motor is mounted close to the axle and transmits power through a reduction a final drive gearbox or final drive.UoS

Tractive Effort

A term for the force applied by traction equipment to accelerate a train.UoS

Trailing Points

Where lines converge in the direction of travel (also see Facing Points)RT


A consist of one or more basic operating units.UoS

Train Control System (US)

American designed software tool for managing train operations.  English, Welsh and Scottish railways intended to use TCS to control its freight operations as a successor of TOPS.UoS

Train Describer

The set of equipment which (except in IECC areas) ensures that the identity of each train is displayed on the signalbox panel together with the indication of that train’s presence.  In these areas the Train Describer circuitry also generates TRUST report data.  Once a train ID has been entered, it is automatically updated in displays when the train entres a new section.RT+UoS

Train Id

Train identifications are displayed electronically to a signaller to supply him or her with the description of approaching trains.  Modern describers use the Four Character Train Identification system (reporting number) such as 1A23.  (see also Head Codes for fuller description)RT+UoS

Train Operated Route Release

A method of releasing a route after passage of a train without further action from the signalman.RT

Train Operated Warning System

Audible warning system, provided over the lineside in locations listed in the sectional Appendix.  When switched on it gives warning of the approach of a train.RT

Train Operator

An organisation authorised and licensed to operate trains over the Network Rail network infrastructure that holds an accepted Railway Operator’s Safety Case and a Rail Operator’s Licence.RT


Part of the integrated operational planning system of Network Rail, produced by Vossloh System Technik Ltd.  (formerly: VST Comreco Rail Ltd.), used for developing train paths which are loaded into the timetable system database (TSDB).  see RailPlan.  RT+UoS

Train Protection and Warning System (TPWS)

Train protection system which, can be fitted on trains which, are wired for AWS.  Coils in the track transmit signal clear / at danger / stop commands but do not provide an uninterrupted beacon sequence.  A first beacon can be used to trigger a timer which stops the train if it is still running when the second beacon is encountered.  UoS

Train Register

A book kept by signallers to record the passage of trains, transmission of bell signals and any exceptional circumstances.RT

Train Running System

Another name for TOPS, the computer system which records details of train running as compared with schedule.  Its offshoot TRUSTDA is the system for recording the size and reason for delays recorded by TRUST.RT

Train Services Database

Holding all available data about planned train services which have been agreed with Railtrack zones throughout the country, ensuring reliable running of the railway network.RT

Train Set

A group of coupled cars including at least one power unit.UoS

Train Staff

A labelled and distinctive piece of wood or metal which must be carried by the driver of a train on a one train working (with train staff) line to ensure no second train can possibly be admitted to the section of line concerned.RT

Train Stop (1)

A train signalling and control system designed to mitigate the consequences of a SPAD by enforced braking and speed control.RT

Train Stop (2)

Mechanical arm located on the wayside, in conjunction with a wayside signal, which causes an emergency brake application when a train passes the signal at danger and the arm is in tripping position.  (Also see Tripcock) UoS+RT

Train Stop (3)

Magnetic equivalent of the mechanical train stop using an arm located on the wayside. The German INDUSI (installed on the Tyne and Wear metro) and the Swiss SIGNUM system are both train stop systems with enhanced capability.  The onboard system may be able to discriminate two or more states of the signalling system thanks to the transmission of different frequencies or polarities.UoS+RT

Transition Curve (UK)

A curve of continuously changing radius and cant to provide a gradual transition between tangent track and a simple curve or between two simple curves.  The curve shape is normally defined by a mathematical expression such as a spiral or a parabola etc. Transition curves are necessary to reduce jerk to a level acceptable to passengers, to guide the wheelsets into the curve and to minimise track forces.  Transition curves are also necessary to change from level to inclined track.  (US: Easement Curve, Spiral Easement, Transition Spiral)UoS

Transitional Curve

The designed parabolic curve linking a straight rail to a full curve.RT

Transmission Based Signalling (TBS)

A system in which the driver is authorised to proceed by radio and, usually, a cab display rather than by observing lineside signals.RT&UoS

Transmission Based Train Control (TBTC)

Generic term for the combination of technologies required to provide a high integrity system of train protection and control which is free of trackside signals.  ETCS level 2 and 3 and West Coast TCS are particular implementation of TBTC.UoS


Track based device to transmit information to a train and, in some cases, to receive information from the train.  See also BaliseUoS.

Transport Operations Rapid Update System

A Racal system giving information on location of public transport vehicles using GPS and TRACE.RT

Transport Radio Asset Control Equipment

A Racal system for monitoring the locations of public transport vehicles to provide input to TORUS.RT

Trap Points

A pair of worked facing switches located at the exit from sidings, goods lines or loops; their purpose being to derail a train leaving without authority and thereby to protect trains on adjacent lines.RT


Removal of ballast with heavy excavation machinery.RT


An electrical switch operated by the train wheels.RT


A device for measuring the adhesion between wheel and rail.RT


A mechanical device mounted on the train that is connected to the emergency braking system.  It is activated by a trainstop if a train passes a signal showing a danger aspect.  If activated, it causes an irretreivable emergency brake application on the train. 


The complete assembly of parts including wheels, axles, bearings, side frames, bolster, brake rigging, springs and all associated connecting components, the function of which is to provide support, mobility and guidance to a railway car or locomotive.  ((UK) Bogie).UoS


The train reporting system based on the TOPS hardware and software.UoS


Delay Attribution the system for recording the size and reason for delays recorded by TRUST.RT


A structure provided to allow a railway line to pass under higher ground, and which has been excavated without disturbing the surface of that ground.RT

Turbo Class 165 and 166

Diesel multiple units operated by Thames Trains and Chiltern Railway.RT

Turbostar Class 170 and 171

Diesel multiple units operated by Central Trains, Midland Mainline Scotrail and Southern Railway.UoS

Turbostar Bombardier (formerly Adtranz)

built diesel mechanical multiple units used nationwide.RT

Turnout (UK)

The trackwork element where a track divides into two.  A turnout normally has two positions, normal and reverse.  The rails are specially shaped to allow a smooth transition from the main track to the diverging track.  The switch rails of the turnout are operated by the point motor or machine and guide the wheels to the reverse or normal direction. The crossing (US: frog) allows the wheels to cross the stock rails (US: switch).  See page 52 for an illustration.UoS+

RT Turnout Number

See Number, Turnout.RT

Turnover Locomotive

A locomotive which waits at a terminal station to take an incoming train away in the opposite direction, where the incoming loco cannot run round the train. The loco which brought the train in then becomes the new turnover locomotive.RT

Twin Block Reinforced Sleeper

A sleeper which consists of two reinforced concrete blocks connected by a steel bar or angle iron.  This features higher longitudinal and lateral resistance to movement than a standard concrete sleeper.UoS


Part of a tamping machine which is pushed (in pairs) into the ballast either side of a sleeper.UoS


UIC Union Internationale des Chemins de Fer, or International Union of Railways.  The European railway regulating body which sets engineering and operating standards for railways. Equivalent to the AAR in the United States.UoS


A bridge crossing under Network Rail property, that is, a bridge which supports the railway.  This includes bridges for roads, footpaths, services, watercourses or industrial use.  Such a bridge will normally support operational tracks.UoS

Underline Bridge

A structure of at least one span of 1.8 metres or more whose main purpose is to carry rail traffic over an obstruction or gap.RT

Unsafe Track Condition

A track irregularity or track condition of such magnitude so as to be specified as requiring immediate action.RT

Up Line

Rail line generally taking trains towards London or the main regional destination, e.g.  Manchester or Glasgow.UoS

Up Relief Line

The Great Western term for the Up Slow Line.RT


Variation Instruction

A record of alteration to dimensions or scope of the contract authorised by the customer’s representative and identifying consequences of alteration.RT

Variation Order

A synonym of variation instruction.RT

Vehicle Change Procedure

One of the Schedules, which form part of the templates for the Track Access Contracts. It relates to what services the TOC wants to run over what routes, detailing the equipment to be used; a procedure exists to apply for a change to these details.RT

Very Short Term Planning

The processing of track access bids received by Operational Planning up to two days before possession.RT


A multispan bridge structure; e.g. Ribblehead.RT

Vital Processor Interlocking (VPI)

Approach to interlocking design, pioneered by General Railway Signal of the USA, involving a single microprocessor which uses mathematical methods to ensure the integrity of the system.UoS


W6W12 Gauge

Loading gauges for standard freight vehicles.  Dimensions are given in the table below for the loading gauges on a range of typical intermodal routes.RT

Unit Type


Swap Body#

Unit Width





Wagon Type









Maximum Unit Height

Feet, Inches















































Table of Loading Gauges applicable to the British Railway Network (NR, 2002)

Waterproofing System

A material or combination of material, including a membrane and where applicable a protective layer, laid to form an impervious barrier to protect the bridge deck from the ingress of water and fuel oil.RT


Everything along the rail line except the operating rail equipment.  UoS


Type of possession established by forcing train services to use alternately different tracks of a multiple track railway (two or more tracks).RT+UoS

Web of Rail (UK)

Space between head and base of a rail occupied by the fish plate at rail joints.UoS

Weekly Operating Notice

contains the engineering work for the forthcoming week and any other information traincrews may require.RT


A device used in the case of a locomotive or vehicle having a wheel which is seized and will not rotate freely, to enable it to be moved clear of a running line. RT


(see Longitudinal Timber.) RT

Welded Vee

Two pieces of rail with parts of the head and foot removed by machining placed either side of a filler plate so as to form a weld preparation, welded using the electroslag welding process and subsequently machined to the drawing requirements.RT

Welwyn Control

A device which must be operated by a signaller before he can clear a section signal when he cannot be give "line clear" from the box in advance.  The object is to make it something he cannot do without thinking.  First introduced after a serious accident at Welwyn Garden City.RT

West Line

The line from Newcastle to Hexham and Carlisle.RT

Wheel Flat

A localised flat area on a steel wheel of a rail vehicle, usually caused by skidding on steel rails, causing a discontinuity in the wheel radius. UoS

Wheel Impact Load Detector

A device which measures the force exerted on the rail by each wheel of a train as it passes and activates an alarm if any are excessive.RT

Wheel Set

A fixed formation of an axle with two wheels set at the correct gauge for the track.  The wheels are pressed onto the axle and rotate with it as a unit.  It is mounted into the bogie (or vehicle) frame with using axle boxes. UoS

Wheel Slide

Synonymous with skidding and usually caused by over braking during poor adhesive conditions. It is a common cause of wheel damage, as it produces a flat spot (called a "flat") on the wheel where the skid occurred.  Severe flats have been known to derail a train. Modern rolling stock is equipped with various systems to assist with the elimination of wheel slide.  These include load control, automatic brake "dumping" if a slide is detected, cosmetic rail applications like Sandite to improve adhesion and attention to maintenance of correct mechanical brake settings. See also our brakes section .UoS

Wheel Slide Protection

A system fitted to most modern passenger rolling stock and traction units which acts in a similar way to ABS, automatically reducing braking effort when wheels start to lockup, thus aiding drivers in conditions where adhesion is poor.RT

Wheel Slip

The phenomenon caused on a locomotive or power vehicle by over application of power to the drive system relative to the available adhesion.  It can cause damage to electric motors and is normally automatically detected to immediately eliminate or reduce the power being applied.  A modern system recently developed using microprocessors is known as creep control and permits a certain degree of slip as this has been proven to improve torque transmission efficiency. UoS

Wheel Slip Protection

A system fitted to most powered passenger rolling stock and traction units which limits tractive effort in conditions where adhesion is poor.RT

Wheel Squeal

The noise produced by wheelrail interaction, particularly on a curve where the radius of curvature is smaller than allowed by the separation of the axles in a wheel set.UoS


A device which is used in the case of a loco or vehicle which has a wheel which is seized and will not rotate freely, to enable it to be moved clear of a running line.RT


(see longitudinal timber.)RT

Whistle Board

A lineside board which indicates to train drivers where they should sound their horns on the approach to a fixed potential hazard.RT


A small gate sometimes provided for pedestrians at a level crossing.RT


A word used in procedural documents to express a requirement to comply with a provision or service. Compare with shall, should, must, may.RT

Witnessing Officer

A member of managerial or professional staff who is not involved in the evaluation, negotiation or contract award process for that particular tender.RT

Working Time Patterns

The framework of working time that is defined by documented rules governing the preparation of rosters.RT

Wrong Side Failure (WSF)

A failure which could cause an unsafe condition, eg.  a red light turning to green (see also the opposite Right Side Failure).  Where a train leaves a station at an earlier than published time, potentially causing passengers to miss the service.RT

Wye (US)

A triangular arrangement of tracks on which locomotives, cars and trains may be turned.UoS



A system of tracks within defined limits provided for making up trains, storing cars, and other purposes, over which movements not authorised by time table or by trainorder may be made, subject to prescribed signals and rules, or special instructions.UoS

Yard Track (US)

A track within a yard used to receive cars for classification for rerouting. UoS


The caution aspect of a signal.RT

Yorkshire Rail Academy

A joint venture between the National Railway Museum and York Technical College, supported by the Learning and Skills Council, for the training of technical staff for the railways.RT

Yellow Book

Publication providing guidance on achieving safety on the railways.  Engineering Safety Management (or the Yellow Book as it is more commonly known) is a handbook designed help people who are involved in changes to the railway (such as new trains and signalling) make sure that these changes contribute to improved safety It is published by the Yellow Book Steering Group.  Details about the Yellow Book can be found here. Yellow Box work which is in the conceptual stage (see also red and green).RT


Zone Hazard Directory

A document which provides, in an easily accessible format, lists of site specific health, safety and environmental hazards to allow contractors and others on Network Rail infrastructure to be aware of the hazards at a particular location and to develop appropriate safe systems of work.RT