Railway Terms

ABAbsolute Block
ABSAbsolute Block System - signalling system, which allows only one train to be in the same section of line (called the block section) at the same time
ABSOLUTE BLOCKThe 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 signaller at the signal box in advance is necessary before a train is allowed to proceed into the Absolute Block section
AC(i) Alternating Current (ii) Area Controller
ACCESS AGREEMENTAn agreement regulated under the Railway Act 1993 setting out the terms and conditions under which companies/ operators obtain access to railway track, stations and certain types of depots
ACCESS CHARGEThe charge paid by railway operators for access to rail facilities, which are the subject of an access agreement
ACCOMMODATION BRIDGEA bridge connecting two areas of land, which were under common ownership but separated when the railway was built
ACCOMMODATION LEVEL CROSSINGPoints at which private roads, public footpaths and bridle paths cross a railway line. There is usually no automatic warning of the approach of a train
ACIAutomatic 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
ADDAutomatic Dropping Device: mechanism, which causes a damaged or displaced pantograph to drop automatically to limit (further) damage to the overhead line equipment
ADJUSTMENT SWITCHA scarf joint installed at the junction of continuous welded rail and jointed track to accommodate expansion of the continuous welded rail track. Adjustment switches are also used to protect track features such as S&C not designed for use in CWR and at the ends of some types of bridges. An adjustment switch is a particular type of expansion device and is also known as an expansion switch.
AHBAutomatic Half Barrier
AHBCAutomatic Half Barrier Crossing
AHBLCAutomatic Half Barrier Level Crossing
ALC(i) Automatic Lining Control (ii) Accommodation Level Crossing
AMSAustenitic Manganese Steel
ANCILLARY MOVEMENTMovements of locomotives and rolling stock directly in association with normal day-to-day train services
AOCLAutomatic Open Level Crossing (locally monitored by train crew)
APCAutomatic Power Control
APM(i) Area Production Manager (ii) Assistant Project Manager
APPAnnual Possession Plan
ARIAlphanumeric Route Indicator
ARLAbove Rail Level
ARM REPEATERElectrical indicator that shows the position of a semaphore signal arm to the controlling signaller
ARSAutomatic Route Setting: information is sent to a computer, which automatically sets the route for trains
ASB(i) As Built (ii) Adjacent Signalbox
ASBPCAdjacent Signalbox Protocol Converter
ASPECTVisual indication of a signal as displayed to the driver
ATAAutomatic Track Alignment
ATOAutomatic Train Operation
ATOCAssociation of Train Operating Companies
ATPAutomatic Train Protection
ATTAAutomatic Track Top and Alignment
ATWSAutomatic Track Warning System
AUTOMATIC LEVEL CROSSINGIncludes AHB, ABCL, AOCL and AOCR level crossings plus those protected by miniature red/green warning lights
AUTOMATIC SIGNALA colour light signal, which operates automatically as trains pass on and off track circuits ahead
AVBAutomatic Vacuum Brake (on rolling stock)
AWBAdvance Warning Board
AWSAutomatic Warning System: 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 COUNTERTrack 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
BALISETrackside train control system transmitter
BALLASTGraded stone sub base used for drainage and support of the track. The advantage is that it is easy to move for maintenance work
BALLAST CLEANINGRemoval 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 REPEATERSignal whose function is to repeat the indication shown by another when the latter cannot be seen by the driver
BARROW CROSSINGLevel crossing at the end of a station platform for use by (or under the supervision of) rail staff only
BASEPLATEMetal casting which supports and holds a flat bottom rail on a sleeper
BAY LINEA dead end line adjacent to a platform
BEARERTimber (or concrete) transverse sleeper supporting the rails in switches and crossings
BH (OR BH RAIL)Bull Head Section Rail: refers to the shape of the rail, which can be one of two types, the other being flat bottomed
BI-DIRECTIONAL LINESLines that are fully signalled to take trains in both directions
BLANKETINGLayer under the ballast to stop clay and soil seeping through
BLOCK BELLSThese 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 CONTROLSEnhancements to the basic block instruments used in Absolute Block area
BLOCK INSTRUMENT/BLOCK INDICATORInstrument, which indicates the state of the line between adjacent (Absolute Block) signal boxes
BLOCK SECTIONThe section of line between the section signal of one signalbox and the home signal of the next signalbox ahead
BLOCK SYSTEMMaintains an interval of space between trains (see also Absolute Block
BLOCKADEThe closure of a route usually to allow engineering works
BMSBasic Mechanical Signalling
BOARDSlang for a signal
BOBBYTraditional slang for a signalman (the original signalmen were actually Railway Police Officers)
BOGEYFrame containing suspension axles and wheels on which a railway vehicle is mounted
BOTTLENECKA location on the network where the number of train movements is close to, or projected to exceed the capacity of that location (same as pinchpoint)
BOWMACConcrete panel which forms part of the road surface over the track at a level crossing
BRAKING DISTANCEThe distance a train needs in which to stop (or to reduce speed) from travelling at a given speed
BRIDGE BASH/STRIKEAn incident where a road vehicle or its load collides with a bridge
BRUFFA company, which makes a vehicle capable of running on both road and rail; normally used to travel by road to aid a derailed rail vehicle
BTETBlock To Electric Traction (turn off, overhead lines and only use diesel trains)
BTPBritish Transport Police
BUFFER STOPAn assembly provided at the end of a terminal track to arrest an overrunning train, designed to take the impact of the train at buffer or coupling height.
CAB SIGNALSignal installed in the driving cab of the train repeating or instead of lineside signals
CANTThe dimension by which the outer rail on a curve is raised above the inner rail
CANT DEFICIENCYFor a train travelling faster than the equilibrium speed on a curve, the theoretical dimension by which the outer rail would need to be raised to reinstate equilibrium
CANT EXCESSFor 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
CANT GRADIENTThe rate at which cant changes in a specific length.
CANTILEVERA type of overhead line support
CAPETrain Cancelled: derived from former telegraphic code
CARRIER DRAINAn impervious drain designed to carry water from place to place instead of collecting water from the surface or surrounding soil directly
CATCable Avoiding Tool
CAT’S EYESSlang term for a position light shunting or subsidiary signal
CATCH POINTSA 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
CATEGORY A SPADAny SPAD when a stop aspect or indication (and any associated preceding indications) was displayed correctly, in sufficient time for a train to be stopped safely at the signal
CATEGORY B SPADAny SPAD when a stop aspect was displayed because: signalling or level crossing equipment had failed or malfunctioned, or it was returned to danger in error
CATENARYTerm given to overhead wires which support the contact wire
CD/RA INDICATORSA special signal to a train driver that a train is ready to depart from a station
CDLA secondary locking system retro-fitted to certain slam door trains and controlled by the guard which prevents passengers from opening the doors
CESSThe 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
CHAINA unit of linear measurement equalling 22 yards or 1/80 of a mile
CHAIRA metal casting, which retains bullhead rail on wooden sleepers
CHECK GAUGEThe distance between the running edge of a running rail and the bearing face of the opposite check rail, measured at right angles to the rails in a plane 14 mm below their top surface.
CHECK RAILA rail or special section provided alongside a running rail at a specified dimension inside gauge to provide a flangeway, to give guidance to wheelsets by restricting lateral movement of the wheels.
CHORD LINEShort section of line connecting two other lines forming a triangle
CIUCentral Interlocking Unit
CLAMPA device used to secure the closed switch of a pair of points to the stock rail. Sometimes known as a clip
CLAMP LOCKA point operating mechanism which locks the points by directly clamping the closed switch rail to the stock rail.
CLAMPLOCK HEATERA cartridge type heater fitted into the clamplock mechanism operating the point’s blades
CLASS 0 TRAINSLight locomotives
CLASS 1 TRAINSExpress passenger trains, mail trains and some emergency trains
CLASS 158 CLASS 170Types of trains
CLASS 2 TRAINSStopping passenger trains
CLASS 3 TRAINSExpress parcel trains
CLASS 4 TRAINSExpress freight trains - 75mph maximum speed
CLASS 5 TRAINSEmpty coaching stock trains
CLASS 6 TRAINSExpress freight trains - 60 mph maximum speed
CLASS 7 TRAINSFreight trains with 45mph maximum speed
CLASS 8 TRAINS(i) Freight trains with 35mph maximum speed (ii) engineers’ trains
CLASS 9 TRAINSA classification formerly abandoned but now in use for EPS and ENS trains
CLASSIFICATIONThe code for a specific type of Complementary Work or Variation
CLIPSee Clamp
CLOCKFACE TIMETABLEA timetable where trains run at regular intervals (e.g. every 10 minutes)
CLOTHOID SPIRAL (TRANSITION CURVE)A transition curve between a straight and a curve where the curvature (the reciprocal of the radius) is proportional to the distance along the curve from its tangent point with the straight.
CONDUCTOR RAILA rail through which DC electricity is supplied to electric trains operating on the third rail system
CONTACT WIREThe overhead wire, which an electric train’s pantograph actually touches in order to draw power
CONTENARYSpecial type of overhead wire used where clearances are tight. The term is a contraction of ‘contact’ wire and ‘catenary’
CONTINUOUS WELDED RAIL (CWRComprises rails welded together to form a single rail length over 36m (120ft), or 55m (180ft) in tunnels with a limited temperature range
COSSController Of Site Safety
COTCondition Of Track
CPCCircuit Protective Conductor
CRIPPLED RAILA rail that has been locally bent by mishandling, derailment or other impact
CRITICAL RAIL TEMPERATUREThe rail temperature to which CWR may be allowed to rise before measures to protect traffic must be taken. The CRT will depend on the stress-free temperature of the rail and the quantity and degree of consolidation of the ballast
CROSSINGA cast or fabricated portion of the track layout which enables the rails of the two tracks to cross each other, while still providing support and guidance for smooth passage of the vehicle’s wheels.
CROSSING VEETwo rails which are joined at an acute angle.
CROSSOVERTwo points, generally of identical geometry, laid back-to-back, enabling trains to cross from one line to another
CROSS-SPAN WIREA wire stretched across tracks holding the overhead line equipment in this desired position
CULVERTSmall bridge or pipe carrying a stream under a railway or road
CURVATUREThe reciprocal of the radius of a curve.
CWRAbbreviation for ‘continuous welded rail’: a) Rails installed in the track that have been welded together to form a single rail greater than a nominal 55 m in length. b) Track constructed with continuous welded rail.
CYCLIC TOPCyclic top is the term used to describe a series of regular dips in the vertical alignment of one or both rails. They may not always be apparent visually because other top irregularities may obscure the cyclic pattern. Cyclic irregularities in track geometry have the potential, when combined with a vehicle’s natural vertical response for a given speed and load, to cause a derailment.
DABBING INEnthusiasts’ jargon for trespassing on the network to take photographs of trains
DALDown Avoiding Line
DATATRAKSemi-automatic 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
DELDown Electric Line
DEMUDiesel Electric Multiple Unit
DEPDesignated Earth Point
DERAILERA device attached to a rail that will, when in its effective position, cause the derailment of a vehicle. It is used to guard against unauthorised movements.
DETECTIONProof 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
DETECTIONA mechanism that proves and provides an output to indicate the actual position of a point end (normal or reverse), and that where fitted, the facing point lock is fully engaged.
DETONATORA 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
DFLDown Fast Line
DGLDown Goods Loop
DIAMOND CROSSINGArrangement of a line wherein the point at which two lines intersect is in the shape of a diamond
DISTANT SIGNALSCautionary 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
DMMUDiesel Mechanical Multiple Unit
DMUDiesel Multiple Unit
DMUDDiesel Multiple Unit Maintenance Depot
DOLLYSlang term for a shunting signal in ex LNER terminology. Sometimes also known as a “Dod” or “Tommy Dodd”
DOODriver Only Operation
DOO (NP)Driver Only Operation - Non-Passenger
DOO (P)Driver Only Operation - Passenger
DOPDriver Only Passenger
DOUBLE END ELECTRICAL SECTIONA section of conductor rail fed from two points
DOUBLE YELLOW ASPECTPreliminary caution signal in four aspect signalling, informing the driver to expect the next main signal to be at single yellow
DOWN LINERail line-taking trains away from London (generally)
DRADriver’s Reminder Appliance: a device in the cab to enable the driver to set a reminder that the signal ahead is at danger
DROPPERComponent of the overhead line electrical equipment, used to keep the contact wire at the correct height
DSDDriver’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”
DSLDown Slow Line
DTSDynamic Track Stabiliser
DUMMYSlang term for a shunting signal (see Ground Disc)
DWLDynamic Warning Lights
DYNAMIC SLEEPER SUPPORT STIFFNESSThe peak load divided by the peak deflection of the underside of a rail seat area of an unclipped sleeper subjected to an approximately sinusoidal pulse load at each railseat; the pulse load being representative in magnitude and duration of the passage of a heavy axle load at high speed, typically 20 tonnes at 100 mph. A falling weight deflectometer can be used to measure dynamic sleeper support stiffness directly.
DYNAMIC TRACK STABILISERA self-propelled ontrack machine for consolidating track ballast by inducing high frequency vibration into the ballast
EBSEmergency Bypass Switch (on rolling stock)
EC4TElectric Current for Traction
ECBEarthing Circuit Breaker
ECCEnglish China Clays
ECMLEast Coast Main Line
ECOElectrical Control Operator
ECR(i) Electrical Control Room: responsible for control of current in the overhead lines (ii) Evaluation of Change Request
ECROElectrical Control Room Operator: the person in charge of a shift in the ECR
ECS(i) Empty Coaching Stock (ii) Enhanced Classic System (=BT)
EDIElectronic Data Interchange
EDPElectrification Distribution and Plant
EECREmergency Electrical Control Room
EFEElectrification Fixed Equipment
EFPLEconomical Facing Point Lock: a mechanism that enables the movement of points and the facing point lock plunger to be operated by the same lever
ELCBEarth Leakage Circuit Breaker
ELUExtra Length Unit: a unit of measurement equivalent to one tenth of a standard length unit, i.e., 2.1 feet (64cm)
ENCAPSULATIONThe bonding of insulating material to a metallic fishplate core under workshop conditions prior to the manufacture of a joint
END POSTMaterial used to insulate rail ends from each other
ENHANCED PERMISSIBLE SPEEDThe permitted speed (higher than the permissible speed) over a section of line which applies to a specific type of train operating at cant deficiencies in excess of those permitted at the permissible speed. Enhanced permissible speeds are detailed in the Sectional Appendix. There may be more than one enhanced permissible speed applicable to a given section of line.
EQUILIBRIUM SPEEDThe speed of a train travelling on a curve which exactly matches the track cant; the speed at which there is neither cant deficiency nor cant excess
ERCUEmergency Rail Cleaning Unit: a hand-held battery powered wire brush system
ESDElectroStatic Discharge
ESIElectricity Supply Industry
ESMEngineering Safety Management
ESMSEngineering Safety Management System
ESOCEmergency Signals On Control
ESREmergency Speed Restriction
ESRPElectrical System Review Panel
ESSDElectroStatic Sensitive Device
ETBElectronic Token Block
ETDNational Extension Trunk Dialling system)
ETMElectric Track Maintenance
ETRElectronic 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)
EWIEmergency Warning Indicator
EXCEEDANCESA further set of measures of track alignment, in addition to track geometry. L2 exceedances include twists, gauge and cyclic irregularities
EXTERNAL COMMANDAn instruction sent to the point operating mechanism by the interlocking to move the point ends to the normal or reverse position.
EZPElectro-Zinc Plating
FACING POINT LOCKA mechanical means of physically locking points in the normal or reverse position so that they cannot be moved other than in response to an external command or manual operation. The lock may be provided independently or incorporated into a point operating mechanism.
FACING POINTSPoints where two routes diverge in the direction of travel (compare with trailing points)
FB (FB RAIL)Flat Bottom rail section, which is used in all modern relaying
FCUField Control Unit
FDDIFibre Distributed Data Interface
FDMFrequency Division Multiplexing
FEATHERSlang term for the row of five white lights mounted at an angle above a (cleared) colour light signal to give an indication of route
FEEDER STATIONA 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
FFFFirst Filament Failure: refers to a failure in a signal lamp, which has more than one filament for safety. The bulb must be replaced, but the signal still works normally and cautioning of trains is not necessary
FIBUFifty Hertz Booster Unit
FISH PLATE (FISHPLATE)Steel plate to secure the ends of two rails together (in jointed track)
FITTED(as of Railway Wagons) – equipped with automatic braking equipment
FIUFailure Indication Unit
FIXED DISTANT SIGNALa distant signal that is only capable of displaying a caution
FLFast Line
FLANGEThe projecting rim of a rail vehicle wheel.
FLANGEWAY GAPThe gap provided to permit the passage of the wheel flanges of rail vehicles, for example between a check rail and a running rail.
FLASH BUTT WELDINGButt weld between rail ends made by a flash welding process damage caused to the surface of a wheel, normally
FLATThe 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
FNFault Number
FOACFibre Optic Adaptor Card
FOG SIGNALSee Detonator
FOOTFALLThe number of people passing through a station
FORI Fibre Optic Route Indicator
FORMATIONMaterial provided between the ballast and the subgrade to either increase or reduce the stiffness of the subgrade, or to prevent overstressing
FOUR FOOTThe area between the inner running faces of a pair of rails
FPLFacing Point Lock: a device to ensure that points, which are facing the approaching trains, are locked in position
FRAMEFault Reporting and Monitoring of Equipment: a system that records signals and telecoms faults
FREE WHEEL PASSAGEThe dimension provided to allow a wheelset to pass through a set of switches or a swing nose crossing, without undesirable contact being made with the wheel flange back and the open switch rail or crossing. In switches this dimension is taken from the back edge of an open switch rail and the running edge of the closed switch rail.
FS(i) Feeder Station (ii) Fixed Stations (trackside radio equipment for cab secure radio)
FSHFull Screen Height
FTSFailure To Stop
FULLY FABRICATED CROSSINGFully fabricated crossings are made by machining rolled rails to produce a point rail and a splice rail fastened together with bolts or multi-groove locking pins. The wing rails are produced from rolled rail and are fastened to the vee by bolts or multi–groove locking pins.
GAINAmplification (especially of a signal)
GAS PRESSURE RAIL WELDINGUsing an oxylacetylere gas for welding rail, a technique used extensively in Japan
GAUGEDistance between the inner running faces of two rails on the same track. Also used to describe two rails on the same track. Also used to describe the “envelope” through which train profiles must fit; this is the structure gauge
GAUGE POINTThe point of intersection of the gauge corner radius and the flat side of the rail head. For 60E1 and BS113A rails this is nominally 14.5 mm below the top of the rail head, measured parallel to the vertical axis of the rail.
GCCGauge Corner Cracking
GEORGEMAS PLUNGERA device permitting the train driver to operate the points at Georgemas Junction
GFGround Frame
GIJGlued Insulated rail Joint
GOODS LINEA line, which has not been signalled to the standards required for running passenger trains
GPLGround Position Light: a low level shunting signal displaying lights rather than a disc
GRADE-SEPARATED JUNCTIONA junction where one track passes over or under another on a bridge to avoid, conflicting train movement
GRICER (slang) a train enthusiast
GROUND DISCSmall shunting signal at low level (often called a ‘dolly’ or ‘dummy’)
GROUND FRAME - SMALL LEVER FRAME, USUALLYSmall 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
GSPGround Switch Panel
GUARDSenior Conductor or Conductor
H/SHand Signaller
HABDHot 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 POINTSPoints, which are worked manually by an adjacent independent lever
HAZCHEMHazardous chemical
HEAD CHECKINGOtherwise known as rolling contact fatigue and gauge corner cracking
HEAD CODEObsolete term for the Train Reporting Number. 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 (e.g. 1A30 is a Class One express train, travelling towards London, No. 30)
HEAD WIDTHThe width of the rail head measured perpendicular to the vertical axis of the rail at the gauge point.
HEADSPAN WIREWire suspended across the tracks and from which the OLE is suspended
HEAT TREATED RAILRail subjected to accelerated cooling or other heat treatment after rolling with the intention of achieving specified mechanical properties
HI CUBE9’6” high transportation container
HMRIHer Majesty’s Railway Inspectorate
HOBCHigh Output Ballast Cleaner
HOME SIGNALThe first stop signal on the approach to a non-TCB signalbox (see TCB)
HSMHand Signalman
HSTHigh Speed Train
HSTRCHigh Speed Track Recording Coach
HTAA type of freight wagon for transporting bulk materials
ILWSInductive Loop Warning System
IMMUNISATION WORKSThese protect the signalling system from high-voltage electric currents in the overhead line train power supply system
IN ADVANCE OFAhead of in the (normal) direction of travel
IN REAR OFBehind in the (normal) direction of travel
INTERLOCKINGInterlocking of points and signals, through the locking frame in the signal box, prevents the accidental setting up of conflicting routes
INTERMEDIATE BLOCK HOME (IBH) SIGNALStop signal controlling exit from an intermediate block section into the block section ahead
INTERMEDIATE BLOCK SECTIONA 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) signalbox
INTERVALThe actual difference in time between trains
IRJInsulated Rail Joint (or a glued joint)
JCT(i) Joint Construction Trades (ii) Jointless Track Circuit
JOINTED TRACKNormal rail in 60ft lengths, but can be 45ft or 30ft lengths. A method of track construction where rails are joined together by fishplates, with an expansion gap between rail ends.
JS1JS1 - basic signalling cable jointing and testing
JS2JS2 - advanced signalling cable jointing and testing
JTCJTC - Jointless Track Circuit
KINEMATIC ENVELOPEThe volume of space swept through by a train in motion. It takes account of overhang on curves, tilting, etc. thus differing from the loading gauge
LAWSLow Adhesion Warning System
LCAMSLow Carbon Austenitic Manganese Steel
LEAF FALL SEASON – APPROXIMATELY 5 WEEKS IN THEApproximately 5 weeks in the autumn when leaves fall on the track requiring measures to assure adhesion
LFCLeaf Contamination: the phenomenon where the action of certain types of leafs being crushed between the rail head and train wheels can cause a build up of residue on rails which can create problems such as wheel slip, impaired braking and failure in the operation of track circuits.
LGSLeaf Guard System
LIGHT LOCOA 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
LIKE FOR LIKE RENEWALThe 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
LINE LIGHTAn indicator on the driver’s 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
LOADING GAUGEThe dimensions of height and width that must not be exceeded by a rail vehicle or its load, so as not to foul lineside fixtures or structures. Similarly, the dimensions in respect to the rails that must not be infringed by such structures.
LOCK STRETCHER BARA bar that connects together the two switch rails of a set of switches and which incorporates or is connected to a bolt which locks the switch rails in the normal or reverse position.
LONGITUDINAL TIMBERLarge 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
LOOPA 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
LOSS OF SECTIONThe reduction in the cross sectional area of a rail, compared to that when new.
LRASLow Rail Adhesion Site
LWRLong Welded Rail: usually delivered to renewal sites in 300’ or 600’ lengths (also known as CWR - continuously welded rail)
LWRTLong Welded Rail Train: the vehicle used to deliver LWR to the work site
MAIN ASPECTThe red, yellow, double yellow, flashing yellow, flashing double yellow or green aspect of a colour light signal
MARKER BOARDDouble-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 (possession).
MEGAFRETAn intermodal wagon with a platform height of 835mm to carry Swap-bodies or containers
MISALIGNMENTDeformation or displacement of a rail or track from its designed alignment.
MSPMeasured Shovel Packing
MSSMaximum Safe Speed
NEW TRACKBEDTrackbed layers placed where there was previously no track. Compare with ‘Renewal (of trackbed)’.
NON-BALLASTED TRACKTrack that is not supported on ballast, including concrete slab track, track supported on longitudinal timbers and directly fastened track on bridges.
NORMAL AND REVERSEThe two defined positions for worked points that are set by the signalling system. The normal and reverse position of each point end is determined by the configuration of the signalling arrangement.
NSKTNo Signaller - Key Token
NSSLNeutral Section Switching Location
NSTRNo Signaller - Token Remote
OBTUSE CROSSINGAn assembly to permit the passage of wheel flanges where two rails intersect at an obtuse angle.
OCCUPATION BRIDGEA bridge carrying a private road, which pre-existed the railway. User rights for the bridge are generally as for the road it carries
OCCUPATION CROSSINGLevel crossing, which does not carry a public road, but one which leads to a farm, factory, etc.
OLEOverhead Line Equipment: the equipment suspended over the railway for supplying electricity to electric trains
ONE TRAIN WORKING (OTW)Signalling on a single line, with or without a train staff, where only one train at a time is permitted
OUTAGEAn outage is an interruption to a service. Planned outages are those that have been scheduled and agreed in advance and the dates and times are published. These outages are used for maintenance and updates to hardware and software.
OUTFALLPlace at which one-drainage system discharges into another drainage system or watercourse
OVERSPEEDThe amount by which the actual speed of a train could exceed the enhanced permissible speed for any reason.
PANTOGRAPHOn train equipment for collecting electricity from overhead power cable
PEE-WEEA warning device for use by personnel on or near the line
PERMANENT WAYThe track structure, which includes rails, sleepers and ballast; any blanketing material (including geotextiles) and associated drainage (also known as P-Way)
PERMANENT WAY COMPONENTA constituent part of the structure of the track including assembly tools and fixtures (but excluding permanent signalling equipment other than stretcher bars), track ballast and sub-ballast material or drainage
PERMISSIBLE SPEEDThe maximum permitted speed over a section of line that applies to trains when not operating at an enhanced permissible speed. Permissible speeds are detailed in the Sectional Appendix.
PERMISSIVE WORKINGPermits 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
PETSPublic Emergency Telephone System
PINCH POINTA location on the rail network where the number of train movements is close to, or projected to exceed, the capacity of that location
PLAIN LINETrack not incorporating switches and crossings. The term ‘plain line’ therefore excludes the through route of S&C.
PLBPossession Limit Board
PLGSPosition Light Ground Signal
PLJIPosition Light Junction Indicator
PLODPatrolman's Lockout Device (trackside staff protection system)
PLSPosition Light Signal
POINT ENDAn item with a movable track component forming one element in a set of points. For the purpose of this document, the term includes a set of switches, one half of a set of switch diamonds, a swing nose crossing, all forms of trap points, a derailer or a scotch block.
POINT MOTORA device used to move the points blades
POINT OPERATING MECHANISMEquipment provided to drive a point end between the normal and reverse positions, using powered or mechanical means.
POINTSThe 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 THROUGHA movement which runs through a trailing set of points which are not set in the correct position for the movement
POSSESSIONA section of line, which is under the exclusive occupation of an Engineer for maintenance or repairs. 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 kept
PPEPersonal Protective Equipment
PRIMARY DRIVEThe point operating mechanism positioned at the toe of points.
PROPELLINGMoving a train using a locomotive at its rear
PROTECTIONIn 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
PSBPower Signal Box
PTSPersonal Track Safety: in relation to the Personal Track Safety Certificate
PUSH-PULLA method of locomotive-hauled train in which the locomotive is permanently attached at one end of the train and when at the rear is remotely controlled from a driver’s cab built into the leading vehicle (see DVT). Its advantage is that run-round moves or turnover locomotives are unnecessary
PWAY (PWAY)See Permanent Way
Q-TRAINSTrains with British Transport Police onboard to combat trespass and vandalism
R/GMiniature red/green warning lights (at level crossing)
RAIL SEATThose areas on the upper face of a sleeper normally between 400mm and 660mm from each end where the rail or chair sits
RAILHEADRunning surface of the rail
RATE OF CHANGE OF CANTThe rate at which a vehicle experiences the change in design cant measured in millimetres per second.
RATE OF CHANGE OF CANT DEFICIENCYThe rate at which a vehicle experiences the change in design cant deficiency measured in millimetres per second.
REACTIONARY DELAYThe delay to trains resulting from an earlier train delay
REFUGEA 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
REGULATESignallers can regulate the train service by giving priority to one train over another; also means levelling the ballast (see also Tamping)
RELAY(i) an electro-mechanical switching device used in many types of signalling systems; it “relays” instructions to signals and points. Relays are now being superseded by Solid State Interlocking (SSI) as used, in particular, in areas controlled by IECC signal boxes (ii) to replace worn out or damaged track
RENEWAL (OF TRACKBED)The replacement of existing trackbed layers or provision of new trackbed layers. For the purposes of this document, renewal includes remodelling, relaying, track lowering and reballasting.
REVERSE CURVETwo abutting curves of opposite flexure or hand.
ROADRailway jargon for railway line
ROLLING CONTACT FATIGUEOn or just below the running surface of a rail caused by the interaction of steel wheels on steel rails
ROLLING STOCKPassenger and freight vehicles, i.e. trains
RULE BOOKA 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.
RUNNING ROUNDTransferring a locomotive from one end of a train to the other by means of a loop
S&CSwitches and Crossings: the specially machined rails designed to permit trains to transfer between tracks
S&C LAYOUTA crossover, turnout, double junction, etc. made up of a number of sub-assemblies complete with all bearers and other components except point motors
S&C UNITHalf or full set of switches, a crossing, check rail, expansion switch, cast crossing or other sub-assembly machined or shaped for a use as part of switches and crossings
S&TSignalling and Telecommunications
SAFETY CRITICAL DEFECTA 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
SANDITEMixture of sand and antifreeze, used for assisting traction adhesion during extreme weather. Sandite S4 also contains steel shot to assist track circuit operation
SANDITE TRAINTrain applying a liquid substance with suspended particles of sand to improve adhesion
SCOTCHA 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
SCOTCH BLOCKA device attached to a rail that will, when in its effective position, prevent the movement of stationary vehicles.
SECTION SIGNALThe stop signal, which controls the entrance to the Block Section (or intermediate block section) ahead (often called the “starter”)
SEMAPHORE SIGNALSSignals usually worked mechanically by wire from a signal box's lever frame, but can be electrically operated; these are mechanical arms rather than coloured lights
SENTINELPersonal Track Safety Identification/Certification System
SETA complete train, including locomotive and carriages, or a multiple unit train
SHOEthe apparatus by which an electric train picks up current from the third rail
SIDE WEARThe reduction in rail head width due to wear caused by flange contact with the rails as trains run around a curved track
SIDEWEARThe loss of head width on the running edge of the rail measured perpendicular to the vertical axis of the rail at the gauge point.
SIGNAL HEADWAYThe minimum interval between trains allowed by the signalling system
SIGNAL SIGHTINGThe viewing of a signal from a train driver’s perspective
SPADSignal Passed at Danger
SQUATA rail specific defect usually visible on the surface of the railhead
STABLINGParking of trains, which are not in use for a period (e.g. overnight)
STANDARD DEVIATIONStandard deviation is a universally used scientific measure of the variation of a random process. Track profiles have been found to have sufficiently similar statistical properties to random processes to enable a measure of the magnitude of track irregularities to be obtained from the standard deviation of the vertical and horizontal profile data. This form of analysis provides track quality indices.
STRESSINGThe process of stretching continuously welded rail so that the stress-free temperature of the rails is within the required range (21 to 27?C)
SUPPLEMENTARY DRIVEA drive provided where necessary in addition to the primary drive to ensure that switch rails or a swing nose crossing are correctly aligned and provide an adequate flangeway gap throughout their length. For the purpose of this document, the term ‘supplementary drive’ includes back drives and supplementary point operating mechanisms.
SWING NOSE CROSSINGA common crossing in which the crossing vee can move laterally to close the flangeway to one or other of the wing rails to provide continuous support to wheelsets. This type of crossing does not require the use of check rails. A swing nose crossing counts as one point end.
SWITCH DIAMONDSA set of switch diamonds consists of two obtuse crossings in which the obtuse point rails are replaced by switch rails and a check rail is not required. A set of switch diamonds counts as two point ends.
SWITCH RAILThe moving portion of rail on each side of a set of points
SWITCH TOEThe end of the switch rail that is traversed first by a vehicle negotiating the switch in the facing direction.
SWITCHESA set of switches consists of two fixed stock rails with their two associated moveable switch rails. A set of switches counts as one point end.
TACHE OVALEA rail fault consisting of a void within the rail, with nothing visible on the exterior. It can be detected with ultrasonic scanning equipment
TAIL LAMPA 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 tail lamp he must stop the train
TAMPINGA process that compacts ballast under sleepers (see also Regulate) to maintain the correct geometry of the track
TCAIDTrack 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
TEN FOOTIdentifies the central space on a four track railway (may actually be less than six feet)
THIRD RAILAn additional rail beside the two running rails used to carry DC power to electrified trains - the alternative to AC (overhead line) electrification
TOKEN (TABLET)A device carried by a Driver as his authority to run over a single line worked by the Electric Token Block System
TONGUE LIPPINGThe deformation of the metal in the planed section of a rail, which forms the switchblade in the turnout, creating a change to the designed profile
TPWSTrain Protection Warning System
TPWS+TPWS functionality at higher speed
TRACK CIRCUITAn electrical device using the rails in an electric circuit, which detects the absence of trains on a defined section of line
TRAILING POINTSWhere lines converge in the direction of travel (also see Facing Points)
TRAIN DESCRIBERThe apparatus that (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
TRANSITIONAL CURVEThe designed parabolic curve linking a straight rail to a full curve
TRAP POINTSFacing points at an exit from a siding or converging line to derail an unauthorised movement
TREADLEElectrical switch operated by the train wheels
TRIBOMETERDevice for measuring the adhesion between wheel and rail
UNDERLINE BRIDGEA 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
UP LINETrack with a normal direction of running generally towards London
WETBEDSDeterioration of sleepers and ballast caused by saturation
WHISTLE BOARDA line sideboard, which indicates to train drivers where they are required to sound a warning