Glossary

- A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z -

A
ABCL	Automatic Barrier Crossing Locally - monitored by train crew
Absolute Block System (ABS)	Signaling system which allows only one train crew to be in the same section of line (called the block section) at the same time.
Absolute Block (AB)	The principle of never having more than one train on the same line in the same section (called the block section) at the same time. The acceptance of a train by the signaler at the signal box in advance is necessary before a train is allowed to proceed into the Absolute Block section.
Accommodation Bridge	A bridge connecting two areas of land which were under common ownership but separated when the railway was built.
Accommodation Level Crossing	Points at which private roads, public roads, public footpaths and bridle paths cross a railway line. There is usually no automatic warning of the approach of a train.
Automatic Dropping Device (ADD)	Mechanism which causes a damaged or displaced pantograph to drop automatically to limit (further) damage.
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.
AF	Auxiliary Feeder.
AHB	Automatic Half Barrier.
AHBC	Automatic Half Barrier Crossing.
AHBLC	Automatic Half Barrier Level Crossing.
ARI	Alphanumeric Route Indicator.
Arm Repeater	Electrical indicator that shows the position of a semaphore signal arm to the controlling signaler.
ARS	Automatic Route Setting: information is sent to a computer which automatically sets the route for trains.
ASLEF	Associated Society of Locomotive Engineers and Fireman - union which represents many train drivers.
Aspect	Visual indication of a signal as displayed to the driver.
ATC	Automatic Train Control.
ATOC	Association of Train Operating Companies.
ATP	Automatic Train Protection.
ATWS	Automatic Track Warning System.
Automatic Level Crossing	Includes AHB, ABCL, AOCL and AOCR level crossings plus those protected by miniature red/green warning lights.
Automatic Signal	A colour light signal which operates automatically as trains pass on and off track circuits ahead.
AVI	Automatic Vehicle Identification: semi-automatic 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 (Total Operations Processing System); generally limited to electricity coal services.
Automatic Warning System (AWS)	Used to give advance warning to drivers of a signal aspect, a temporary speed restriction or a permanent speed restriction more than 30% slower than the current limit.
Axle counter	Track mounted equipment which counts the number of axles entering and leaving the track section at each extremity. A calculation is performed to determine whether the track is occupied or clear.

B
Balise	Trackside train control system transmitter.
Ballast	Graded stone sub-base used for drainage and support of the track. The advantage is that it is easy to move for maintenance work.
Ballast Cleaning	Removal of existing ballast using a machine which grades the excavated ballast, returning good stone to the track and takes fine stone and spoil for disposal.
Banner Repeater	Signal whose function is to repeat the indication shown by another when the latter cannot be seen by the driver.
Barrow Crossing	Level crossing at the end of a station platform for use by (or under the supervision of) rail staff only.
Bay Line	A dead end line adjacent to a platform.
Bi-Directional Lines	Lines that are fully signaled to take trains in both directions.
Blockade	The closure of a route usually to allow engineering works.
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.
Block Controls	Enhancements to the basic block instruments used in an Absolute Block area.
Block Instrument / Block Indicator	Instrument which indicates the state of the line between adjacent (Absolute Block) signal boxes.
Block Section	The section of line between the section signal of one signal box and the home signal of the next signal box ahead.
Bogey	Frame containing suspension axles and wheels on which a railway vehicle is mounted.
Bowmac	Concrete panel forming part of the road surface over the track at a level crossing.
Braking Distance	The distance a train needs in which to stop (or to reduce speed) from travelling at a given speed.
Bridge Strike	An incident where a road vehicle or its load collides with a bridge.

C
Cant	The dimension by which the outer rail on a curve is raised above the inner rail.
Category A SPaD	When a stop aspect, end of in-cab signaled movement authority, or indication (and any associated preceding cautionary indications), was displayed correctly, in sufficient time for the train to be stopped safely at the signal or end of in-cab movement authority.
Category B SPaD	When a stop aspect, end of in-cab signaled movement authority, which previously showed a proceed indication, was displayed because: of infrastructure failure (for example, signaling or level crossing equipment has failed or malfunctioned) it was returned to danger in error.
Category C SPaD	When a stop aspect, end of in-cab signaled movement authority or indication was not displayed in sufficient time for the train to be stopped safely at the signal because it was returned to danger automatically or in an emergency.
Category D SPaD	When vehicles without any traction unit attached, or a train which is unattended, run away past a signal which is at danger or without an in-cab movement authority.
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 an equipment requirement before all vehicles had automatic brakes.
Catenary	Term given to overhead wires which support the contact wire.
CB	Circuit Breaker.
CCTV	Closed Circuit Television: often used for station security and monitoring level crossings.
CD/RA Indicators	A special signal to a train driver that a train is ready to depart from a station.
Cess	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.
Chain	A unit of linear measurement equaling 22 yards or 1/80 of a mile.
Chair	A metal casting, this retains bullhead rail on wooden sleepers.
CIRAS	Confidential Incident Reporting and Analysis System.
Clamp, clamplock	(i) a device used to secure the closed switch of a pair of points to the stock rail. Sometimes known as a clip. (ii) a point operating mechanism, which locks the points by directly clamping the closed switch rail to the stock rail.
Clamplock heater	A cartridge type heater fitted to the clamplock mechanism operating the point's blades.
CMS	Competence Management System.
Conductor Rail	A rail through which DC electricity is supplied to electric trains operating on a third rail system.
Contact Wire	The overhead wire, which an electric train's pantograph actually touches in order to draw power.
COSHH	Control of Substances Hazardous to Health Regulations 1988.
COSS	Controller of Site Safety.
Crossing	The component of a turnout that enables a train wheel to complete the transfer from one line to another. It is this unit that enables the wheel to cross the original line being traversed.
Crossover	Two points, generally of identical geometry, laid back-to-back, enabling trains to cross from one line to another.
Cross-Span Wire	A wire stretched across tracks holding the overhead line equipment in this desired position.
CSR	Cab Secure Radio.

D
DEMU	Diesel Electric Multiple Unit.
Detection	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 released.
Detonator	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. Correctly known as a railway fog signal.
DfT	Department for Transport.
DG/DGI	Dangerous Goods / Dangerous Goods Incident.
Diamond Crossing	Arrangement of a line wherein the point at which two lines intersect is in the shape of a diamond.
Distant Signals	Cautionary Signals at which a train does not have to stop, and which therefore do not have a red aspect; when "on" they are a warning that the next aspect could be red.
DO	Driver Only.
DOO	Driver Only Operation.
DMG (Driver Management Group)	Provides a forum for the discussion and exchange of ideas, good practice and the identification and development of key issues.
DMU	Diesel Multiple Unit.
DRA	Driver's Reminder Appliance; a device in the cab to enable the driver to set a reminder that the signal ahead is at danger.
Dropper	Component of the overhead line electrical equipment, used to keep the contact wire at the correct height.
DSD	Driver's Safety Device: device on traction rolling stock that will stop the train if the driver becomes incapacitated. Popularly known as the 'Deadman's Pedal' or 'Deadman's Handle'.
DVT	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 push-pull working.

E
EMU	Electric Multiple Unit.
ERTMS	European Rail Traffic Management System.
ETB	Electronic Token Block.
ETRB	Electronic Train Register Block: PC based system installed in manual.
RWI	Emergency Warning Indicator.

F
Facing Points	Points where two routes diverge in the direction of travel (compare with trailing points).
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 is supplied.
Fish Plate	Steel plate to secure the ends of two rails together (in jointed track).
Fixed Distant Signal	A distant signal that is only capable of displaying a caution.
Flat	The rail equivalent to a tyre puncture. It is the damage caused to the surface of a wheel, normally caused by skidding; corrected only by using a wheel lathe to restore the correct curvature.
Fog Signal	See Detonator.
Four Foot	The area between the inner running faces of a pair of rails.
FPL	Facing Point Lock: a device to ensure that points, which are facing approaching train, are locked in position.
Franchise	An agreement between the Franchising Director and a train operator to run particular passenger services for a defined period.
FS	Feeder Station.

G
Gauge	Distance between the inner running faces of two rails on the same track. Also used to describe the "envelope" through which train profiles must fit; this is the structure gauge.
Goods Line	A line which has not been signaled to the standards required for running passenger trains.
GPL	Ground Position Light: a low level shunting signal displaying lights rather than a disc.
GPS	(i) Global Positioning by Satellite (ii) Global Positioning System.
Green Card	Common name for the green defective vehicle label , which is put on a railway vehicle considered fit to travel within limitations i.e. only to place of repair and with restrictions on speed or braking conditions, etc.
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.
Ground Frame	Small lever frame, usually mounted at ground level or sometimes a small switch panel, used to work little used connections at locations remote from the signal box.
GSM-R	European Radio System for Railways.

H
HABD	Hot Axle Box Detector: a sleeper mounted temperature detector which warns a signal box of an overheated bearing as it counts the passing wheels. It indicates which axle is faulty, if one axle or wheel is hotter than the others on the train.
Hand Points	Points, which are worked manually by an adjacent independent lever.
HAZCHEM	Hazardous Chemical.
HST	High Speed Train.

I
IBJ	Insulated Block Joint (see also IRJ).
IECC	Integrated Electronic Control Centre: a power signal box where all data displays, safety interlocking, etc are computer controlled and under normal circumstances trains are signaled automatically according to the TRUST Train ID.
IMC	Infrastructure Management Company.
Interlocking	Interlocking of points and signals through the locking frame in the signal box, prevents the accidental setting up of conflicting routes.
Intermediate Block Home (IBH)	Stop signal controlling exit from an intermediate block section into the block section ahead.
Intermediate Block Section	A track-circulated 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.
Interoperability	A European initiative to promote a single market in the rail sector by removing the technical problems involved in running trains between member states.

L
LAWS	Low Adhesion Warning System.
Leaf Fall Season	Approximately 9 weeks in the autumn when leaves fall on the track requiring measures to assure adhesion.
LX	(L/X) Level Crossing.

M
Mechanical & Electrical Engineering / Engineer	The Mechanical and Electrical Engineers (M&EE) Networking Group is a bi-monthly meeting that promotes good practice and reduces incidents associated with On Track Machines (OTM).
Main Aspect	The red, yellow, double yellow, flashing yellow, flashing double yellow or green aspect of a colour light signal.
Marker Board	Double-sided yellow board with two vertical red-yellow flashing lights on one side and two yellow flashing lights on the other used to indicate a work site: (i) Possession (red lights) (ii) Work Site (yellow lights). Possession and work sites are not necessarily the same.
MSS	Multi-SPaD signal.

O
OFG	Operations Focus Group (OFG) facilitates the progressive improvement of operational safety through understanding and development and promotion of justifiable and effective campaigns, programmes and tools.
OHILE	Overhead Line Equipment: the equipment suspended over the railway for supplying electricity to electric trains.
One Train Working (OTW)	Signaling on a single line, with or without train staff, where only one train at a time is permitted.
OPSRAM	Route Operational Risk Reduction and Mitigation (OPSRAM) Groups are bi-monthly meetings facilitated by Network Rail and are a means by which route operators can meet at a route level to coordinate operational risk reduction and mitigation activity, and share good practice in the management of operational issues.
ORR	Office of Railway Regulation.
OTM	On-Track Machine.
OTDR	On Train Data Recorder.
Overbridge	A bridge that crosses over the railway.
Overlap	The distance beyond a stop signal which must be clear before a train can normally be allowed to approach the signal.

P
Permanent Way / P-Way	The track structure, which includes rails, sleepers and ballast; any blanketing material (including geotextiles) and associated drainage (also known as P-Way).
Pantograph	On train equipment, for collecting electricity from overhead power cable.
PICOP	Person in Charge of Possession.
Points	The items of permanent way which may be aligned to one of two positions, normal or reverse, according to the direction of train movement required.
Points Run Through	A movement which runs through a trailing set of points which are not set in the correct position for the movement.
Power Operated Points	Points operated by a means other than mechanical (e.g. electric motor, hydraulics or compressed air).
PPE	Personal Protective Equipment.
PTS	Personal Track Safety.

R
Rail Accident Investigation Board (RAIB)	The Rail Accident Investigation Board (RAIB) is the independent railway accident investigation organisation for the UK. It investigates railway accidents and incidents on the UK's railways to improve safety, not to establish blame.
Rail Safety and Standards Board (RSSB)	RSSB build industry-wide consensus and facilitates the resolution of difficult cross-industry issues. It is a not-for-profit company owned by major industry stakeholders. It is independent of any single railway company and their commercial interests.
Railway Group Standard (RGS)	A Railway Group Standard (RGS) is a document produced pursuant to the Railway Group Standards Code (the Code) (or equivalent predecessor documents, including previous versions of the Code) defining mandatory requirements in respect of the mainline railway.
Refuge	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 safely.
RIDDOR	An abbreviation of 'Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995'.
Right side Failure	A mode of failure which causes a piece of equipment to cease functioning without compromising the safety of trains.
RIMINI	Risk minimisation.
RMT	National Union of Rail, Maritime and Transport Workers.
Railway and Other Guided Transport Systems Regulations (ROGS)	Contain much of the safety regulation for railways and other guided transport modes. The regulations require most railway operators to maintain a safety management system (SMS) and hold a safety certificate or authorisation indicating the SMS has been accepted by the Office of Rail Regulation. ROGS also update the legal requirements for the management of safety critical work.
Rolling Stock	Passenger and freight vehicles i.e. trains.
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 12 volumes, each one "personalised" by job type e.g. No.3 Signalman, No.4 Train Driver etc.

S
Safety Management System	A proven system which when followed enables a company to perform tasks at all levels of the organisation safely. 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.
Semaphore Signals	Signals usually worked mechanically by a wire from a signal box's lever frame, but can be electrically operated; these are mechanical arms rather than coloured lights.
Sentinel	Personal Track Safety Identification / Certification System.
Shunting Signal	A signal, this is provided for shunting purposes only.
Signal Sighting	The viewing of a signal from a train driver's perspective.
Sleeper	Wood, concrete or steel object, which holds the rails apart and supports the track on the ballast.
SLW	Single Line Working.
SPAD	Signal Passed at Danger.
Stabling	Parking of trains which are not in use for a period (e.g. overnight).
Standard	Railway Group Standard - a document established by consensus and approved by a recognised body that provides, for common and repeated use, rule, guidelines or characteristics for activities or their results, aimed at achieving the optimum degree or order in a given context.
Stop Block	A buffer stop.
Stop Signal	Any main signal which can display a stop aspect or indication.

T
T&RS	Traction and Rolling Stock.
Tail Lamp	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 signaler sees a train pass without a tail lamp he must stop the train.
TBW	Temporary Block Working.
TC	Track Circuit.
TCA	Track Circuit Actuator: a device fitted to some vehicles to improve the operation of track circuits.
TCB	Track Circuit Block.
TCF	Track Circuit Failure.
Ten Foot	Identifies the central space on a four track railway (may actually be less than six feet).
Third Rail	An additional rail beside two running rails used to carry DC power to electrified trains - the alternative to AC (overhead line) electrification.
TIS	Traction Interlock Switch.
TNC	Temporary Non-Compliance.
Token (tablet)	A device carried by a driver as his authority to run over a single line worked by the Electric Token Block System.
Top and Tail working	Running trains with an engine at each end, usually during disruption to avoid time consuming running-round movements.
TOWS	Train Operating Warning System: gives audible warning of the approach of a train.
TPS	Train Power Supply.
TPT	Train Positioning and Tracking.
TPWS	Train Protection Warning System.
Track Circuit (TC)	An electrical device using the rails in an electric circuit which detects the absence of trains on a defined section of line.
Track Circuit Block (TCB)	A modification of the Absolute Block System, employing track circuiting throughout. A train may proceed, as soon as the line is clear, to the next stop signal plus the required overlap beyond that signal.
Trailing Points	Where lines converge in the direction of travel (see also Facing Points).
Train Describer	The apparatus that (except in IECC areas) ensures that the identity of each train is displayed on the signal box panel together with the indication of that train's presence. In these areas the Train Detector circuitry also generates TRUST report data.
Train ID	Train identification displayed electronically to a signaler.
Train Plan	Used for developing train paths.
Train Path	The planned schedule over the network for a train.
Train Register	A book kept by signalers to record the passage of trains, transmission of bell signals and any exceptional circumstances.
Transitional Curve	The designed parabolic curve linking a straight curve to a full curve.
Trap Points	Facing points at an exit from a siding or converging line to derail an unauthorised movement.
Treadle	Electrical switch operated by the train wheels.
Tribometer	Device for measuring an adhesion between wheel and rail.
TRU	Track Recording Unit.
TRUST	Train Running System on TOPS (Total Operating Processing System): computer system, which records details of train running as compared with schedule.
TSI	Technical Specification for Interoperability.
TSR	Temporary Speed Reduction.
TSS	Train Stop Sensors.
TSSA	Transport Salaried Staffs Association (a union for salaried staff).
Tunnel	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.

U
Underbridge	A bridge crossing under Network Rail property. This includes bridges for roads, footpaths, services, watercourses or industrial use. Such a bridge will normally support operational tracks.
UWC	User Worked Crossing.

V
VAB	Vehicle Acceptance Board.
VDU	Visual Display unit for computers.
Viaduct	A multi-span bridge structure.
Very Short Term Plan (VSTP)	The processing of track access bids received by Operational Planning up to two days before possession.

W
Wheel / Rail Interface Systems Authority	A cross industry body founded to manage the interface between train wheels.
Wheelskate	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.
Whistle Board	A line sideboard, which indicates to train drivers where they are required to sound a warning.
Wicket	A small gate sometimes provided for pedestrians at a level crossing.
WON	Weekly Operating Notice: contains the engineering work.
Wrong Side Failure	See WSF.
WSF	(i) Wrong side failure: something which fails in an unsafe condition, (ii) Wrong side signaling failure.

Y
Yellow Peril	A notice issued (on yellow paper) to operating staff giving information usually about a new individual signaling diagram.