| Term | Meaning |
|---|---|
| AB | Absolute Block |
| ABS | Absolute 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 BLOCK | 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 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 AGREEMENT | An 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 CHARGE | The charge paid by railway operators for access to rail facilities, which are the subject of an access agreement |
| 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 footpaths and bridle paths cross a railway line. There is usually no automatic warning of the approach of a train |
| ACI | 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 |
| ADD | Automatic Dropping Device: mechanism, which causes a damaged or displaced pantograph to drop automatically to limit (further) damage to the overhead line equipment |
| ADJUSTMENT SWITCH | A 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. |
| AHB | Automatic Half Barrier |
| AHBC | Automatic Half Barrier Crossing |
| AHBLC | Automatic Half Barrier Level Crossing |
| ALC | (i) Automatic Lining Control (ii) Accommodation Level Crossing |
| AMS | Austenitic Manganese Steel |
| ANCILLARY MOVEMENT | Movements of locomotives and rolling stock directly in association with normal day-to-day train services |
| AOCL | Automatic Open Level Crossing (locally monitored by train crew) |
| APC | Automatic Power Control |
| APM | (i) Area Production Manager (ii) Assistant Project Manager |
| APP | Annual Possession Plan |
| ARI | Alphanumeric Route Indicator |
| ARL | Above Rail Level |
| ARM REPEATER | Electrical indicator that shows the position of a semaphore signal arm to the controlling signaller |
| ARS | Automatic Route Setting: information is sent to a computer, which automatically sets the route for trains |
| ASB | (i) As Built (ii) Adjacent Signalbox |
| ASBPC | Adjacent Signalbox Protocol Converter |
| ASPECT | Visual indication of a signal as displayed to the driver |
| ATA | Automatic Track Alignment |
| ATO | Automatic Train Operation |
| ATOC | Association of Train Operating Companies |
| ATP | Automatic Train Protection |
| ATTA | Automatic Track Top and Alignment |
| 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 |
| AVB | Automatic Vacuum Brake (on rolling stock) |
| AWB | Advance Warning Board |
| AWS | Automatic 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 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 |
| 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 |
| BASEPLATE | Metal casting which supports and holds a flat bottom rail on a sleeper |
| BAY LINE | A dead end line adjacent to a platform |
| BEARER | Timber (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 LINES | Lines that are fully signalled to take trains in both directions |
| BLANKETING | Layer under the ballast to stop clay and soil seeping through |
| 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 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 signalbox and the home signal of the next signalbox ahead |
| BLOCK SYSTEM | Maintains an interval of space between trains (see also Absolute Block |
| BLOCKADE | The closure of a route usually to allow engineering works |
| BMS | Basic Mechanical Signalling |
| BOARD | Slang for a signal |
| BOBBY | Traditional slang for a signalman (the original signalmen were actually Railway Police Officers) |
| BOGEY | Frame containing suspension axles and wheels on which a railway vehicle is mounted |
| BOTTLENECK | A 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) |
| BOWMAC | Concrete panel which forms 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 BASH/STRIKE | An incident where a road vehicle or its load collides with a bridge |
| BRUFF | A 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 |
| BTET | Block To Electric Traction (turn off, overhead lines and only use diesel trains) |
| BTP | British Transport Police |
| BUFFER STOP | An 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 SIGNAL | Signal installed in the driving cab of the train repeating or instead of lineside signals |
| CANT | The dimension by which the outer rail on a curve is raised above the inner rail |
| CANT DEFICIENCY | For 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 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 |
| CANT GRADIENT | The rate at which cant changes in a specific length. |
| CANTILEVER | A type of overhead line support |
| CAPE | Train Cancelled: derived from former telegraphic code |
| CARRIER DRAIN | An impervious drain designed to carry water from place to place instead of collecting water from the surface or surrounding soil directly |
| CAT | Cable Avoiding Tool |
| CAT’S EYES | Slang term for a position light shunting or subsidiary signal |
| 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 |
| CATEGORY A SPAD | Any 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 SPAD | Any 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 |
| CATENARY | Term given to overhead wires which support the contact wire |
| CD/RA INDICATORS | A special signal to a train driver that a train is ready to depart from a station |
| CDL | A secondary locking system retro-fitted to certain slam door trains and controlled by the guard which prevents passengers from opening the doors |
| 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 equalling 22 yards or 1/80 of a mile |
| CHAIR | A metal casting, which retains bullhead rail on wooden sleepers |
| CHECK GAUGE | The 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 RAIL | A 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 LINE | Short section of line connecting two other lines forming a triangle |
| CIU | Central Interlocking Unit |
| CLAMP | A device used to secure the closed switch of a pair of points to the stock rail. Sometimes known as a clip |
| CLAMP LOCK | 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 into the clamplock mechanism operating the point’s blades |
| CLASS 0 TRAINS | Light locomotives |
| CLASS 1 TRAINS | Express passenger trains, mail trains and some emergency trains |
| CLASS 158 CLASS 170 | Types of trains |
| CLASS 2 TRAINS | Stopping passenger trains |
| CLASS 3 TRAINS | Express parcel trains |
| CLASS 4 TRAINS | Express freight trains - 75mph maximum speed |
| CLASS 5 TRAINS | Empty coaching stock trains |
| CLASS 6 TRAINS | Express freight trains - 60 mph maximum speed |
| CLASS 7 TRAINS | Freight trains with 45mph maximum speed |
| CLASS 8 TRAINS | (i) Freight trains with 35mph maximum speed (ii) engineers’ trains |
| CLASS 9 TRAINS | A classification formerly abandoned but now in use for EPS and ENS trains |
| CLASSIFICATION | The code for a specific type of Complementary Work or Variation |
| CLIP | See Clamp |
| CLOCKFACE TIMETABLE | A 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 RAIL | A rail through which DC electricity is supplied to electric trains operating on the third rail system |
| CONTACT WIRE | The overhead wire, which an electric train’s pantograph actually touches in order to draw power |
| CONTENARY | Special type of overhead wire used where clearances are tight. The term is a contraction of ‘contact’ wire and ‘catenary’ |
| CONTINUOUS WELDED RAIL (CWR | Comprises rails welded together to form a single rail length over 36m (120ft), or 55m (180ft) in tunnels with a limited temperature range |
| COSS | Controller Of Site Safety |
| COT | Condition Of Track |
| CPC | Circuit Protective Conductor |
| CRIPPLED RAIL | A rail that has been locally bent by mishandling, derailment or other impact |
| CRITICAL RAIL TEMPERATURE | The 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 |
| CROSSING | A 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 VEE | Two rails which are joined at an acute angle. |
| 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 |
| CULVERT | Small bridge or pipe carrying a stream under a railway or road |
| CURVATURE | The reciprocal of the radius of a curve. |
| CWR | Abbreviation 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 TOP | Cyclic 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 IN | Enthusiasts’ jargon for trespassing on the network to take photographs of trains |
| DAL | Down Avoiding Line |
| DATATRAK | Semi-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 |
| DEL | Down Electric Line |
| DEMU | Diesel Electric Multiple Unit |
| DEP | Designated Earth Point |
| DERAILER | A 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. |
| 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 cleared |
| DETECTION | A 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. |
| 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 |
| DFL | Down Fast Line |
| DGL | Down Goods Loop |
| 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 |
| DMMU | Diesel Mechanical Multiple Unit |
| DMU | Diesel Multiple Unit |
| DMUD | Diesel Multiple Unit Maintenance Depot |
| DOLLY | Slang term for a shunting signal in ex LNER terminology. Sometimes also known as a “Dod” or “Tommy Dodd” |
| DOO | Driver Only Operation |
| DOO (NP) | Driver Only Operation - Non-Passenger |
| DOO (P) | Driver Only Operation - Passenger |
| DOP | Driver Only Passenger |
| DOUBLE END ELECTRICAL SECTION | A section of conductor rail fed from two points |
| DOUBLE YELLOW ASPECT | Preliminary caution signal in four aspect signalling, informing the driver to expect the next main signal to be at single yellow |
| DOWN LINE | Rail line-taking trains away from London (generally) |
| 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” |
| DSL | Down Slow Line |
| DTS | Dynamic Track Stabiliser |
| DUMMY | Slang term for a shunting signal (see Ground Disc) |
| DWL | Dynamic Warning Lights |
| DYNAMIC SLEEPER SUPPORT STIFFNESS | The 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 STABILISER | A self-propelled ontrack machine for consolidating track ballast by inducing high frequency vibration into the ballast |
| EBS | Emergency Bypass Switch (on rolling stock) |
| EC4T | Electric Current for Traction |
| ECB | Earthing Circuit Breaker |
| ECC | English China Clays |
| ECML | East Coast Main Line |
| ECO | Electrical Control Operator |
| ECR | (i) Electrical Control Room: responsible for control of current in the overhead lines (ii) Evaluation of Change Request |
| ECRO | Electrical Control Room Operator: the person in charge of a shift in the ECR |
| ECS | (i) Empty Coaching Stock (ii) Enhanced Classic System (=BT) |
| EDI | Electronic Data Interchange |
| EDP | Electrification Distribution and Plant |
| EECR | Emergency Electrical Control Room |
| EFE | Electrification Fixed Equipment |
| EFPL | 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 |
| ELCB | Earth Leakage Circuit Breaker |
| ELU | Extra Length Unit: a unit of measurement equivalent to one tenth of a standard length unit, i.e., 2.1 feet (64cm) |
| ENCAPSULATION | The bonding of insulating material to a metallic fishplate core under workshop conditions prior to the manufacture of a joint |
| END POST | Material used to insulate rail ends from each other |
| ENHANCED PERMISSIBLE SPEED | The 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 SPEED | The 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 |
| ERCU | Emergency Rail Cleaning Unit: a hand-held battery powered wire brush system |
| ESD | ElectroStatic Discharge |
| ESI | Electricity Supply Industry |
| ESM | Engineering Safety Management |
| ESMS | Engineering Safety Management System |
| ESOC | Emergency Signals On Control |
| ESR | Emergency Speed Restriction |
| ESRP | Electrical System Review Panel |
| ESSD | ElectroStatic Sensitive Device |
| ETB | Electronic Token Block |
| ETD | National Extension Trunk Dialling system) |
| ETM | Electric Track Maintenance |
| ETR | 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) |
| EWI | Emergency Warning Indicator |
| EXCEEDANCES | A further set of measures of track alignment, in addition to track geometry. L2 exceedances include twists, gauge and cyclic irregularities |
| EXTERNAL COMMAND | An instruction sent to the point operating mechanism by the interlocking to move the point ends to the normal or reverse position. |
| EZP | Electro-Zinc Plating |
| FACING POINT LOCK | A 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 POINTS | Points 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 |
| FCU | Field Control Unit |
| FDDI | Fibre Distributed Data Interface |
| FDM | Frequency Division Multiplexing |
| FEATHER | Slang 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 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 |
| FFF | First 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 |
| FIBU | Fifty 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 |
| FIU | Failure Indication Unit |
| FIXED DISTANT SIGNAL | a distant signal that is only capable of displaying a caution |
| FL | Fast Line |
| FLANGE | The projecting rim of a rail vehicle wheel. |
| FLANGEWAY GAP | The 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 WELDING | Butt weld between rail ends made by a flash welding process damage caused to the surface of a wheel, normally |
| 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 |
| FN | Fault Number |
| FOAC | Fibre Optic Adaptor Card |
| FOG SIGNAL | See Detonator |
| FOOTFALL | The number of people passing through a station |
| FORI | Fibre Optic Route Indicator |
| FORMATION | Material provided between the ballast and the subgrade to either increase or reduce the stiffness of the subgrade, or to prevent overstressing |
| 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 the approaching trains, are locked in position |
| FRAME | Fault Reporting and Monitoring of Equipment: a system that records signals and telecoms faults |
| FREE WHEEL PASSAGE | The 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) |
| FSH | Full Screen Height |
| FTS | Failure To Stop |
| FULLY FABRICATED CROSSING | Fully 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. |
| GAIN | Amplification (especially of a signal) |
| GAS PRESSURE RAIL WELDING | Using an oxylacetylere gas for welding rail, a technique used extensively in Japan |
| GAUGE | Distance 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 POINT | The 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. |
| GCC | Gauge Corner Cracking |
| GEORGEMAS PLUNGER | A device permitting the train driver to operate the points at Georgemas Junction |
| GF | Ground Frame |
| GIJ | Glued Insulated rail Joint |
| GOODS LINE | A line, which has not been signalled to the standards required for running passenger trains |
| GPL | Ground Position Light: a low level shunting signal displaying lights rather than a disc |
| GRADE-SEPARATED JUNCTION | A junction where one track passes over or under another on a bridge to avoid, conflicting train movement |
| GRICER | (slang) a train enthusiast |
| GROUND DISC | Small shunting signal at low level (often called a ‘dolly’ or ‘dummy’) |
| GROUND FRAME - SMALL LEVER FRAME, USUALLY | 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 |
| GSP | Ground Switch Panel |
| GUARD | Senior Conductor or Conductor |
| H/S | Hand Signaller |
| 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 |
| HEAD CHECKING | Otherwise known as rolling contact fatigue and gauge corner cracking |
| HEAD CODE | Obsolete 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 WIDTH | The width of the rail head measured perpendicular to the vertical axis of the rail at the gauge point. |
| HEADSPAN WIRE | Wire suspended across the tracks and from which the OLE is suspended |
| HEAT TREATED RAIL | Rail subjected to accelerated cooling or other heat treatment after rolling with the intention of achieving specified mechanical properties |
| HI CUBE | 9’6” high transportation container |
| HMRI | Her Majesty’s Railway Inspectorate |
| HOBC | High Output Ballast Cleaner |
| HOME SIGNAL | The first stop signal on the approach to a non-TCB signalbox (see TCB) |
| HSM | Hand Signalman |
| HST | High Speed Train |
| HSTRC | High Speed Track Recording Coach |
| HTA | A type of freight wagon for transporting bulk materials |
| ILWS | Inductive Loop Warning System |
| IMMUNISATION WORKS | These protect the signalling system from high-voltage electric currents in the overhead line train power supply system |
| IN ADVANCE OF | Ahead of in the (normal) direction of travel |
| IN REAR OF | Behind in the (normal) direction of travel |
| 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) SIGNAL | Stop signal controlling exit from an intermediate block section into the block section ahead |
| 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) signalbox |
| INTERVAL | The actual difference in time between trains |
| IRJ | Insulated Rail Joint (or a glued joint) |
| JCN | Junction |
| JCT | (i) Joint Construction Trades (ii) Jointless Track Circuit |
| JOINTED TRACK | Normal 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. |
| JS1 | JS1 - basic signalling cable jointing and testing |
| JS2 | JS2 - advanced signalling cable jointing and testing |
| JTC | JTC - Jointless Track Circuit |
| 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 loading gauge |
| LAWS | Low Adhesion Warning System |
| LCAMS | Low Carbon Austenitic Manganese Steel |
| LEAF FALL SEASON – APPROXIMATELY 5 WEEKS IN THE | Approximately 5 weeks in the autumn when leaves fall on the track requiring measures to assure adhesion |
| LFC | Leaf 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. |
| LGS | Leaf Guard System |
| LIGHT LOCO | 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 |
| 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 |
| LINE LIGHT | An 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 GAUGE | The 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 BAR | A 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 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 |
| LOOP | 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 |
| LOSS OF SECTION | The reduction in the cross sectional area of a rail, compared to that when new. |
| LRAS | Low Rail Adhesion Site |
| LWR | Long Welded Rail: usually delivered to renewal sites in 300’ or 600’ lengths (also known as CWR - continuously welded rail) |
| LWRT | Long Welded Rail Train: the vehicle used to deliver LWR to the work site |
| 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 (possession). |
| MEGAFRET | An intermodal wagon with a platform height of 835mm to carry Swap-bodies or containers |
| MISALIGNMENT | Deformation or displacement of a rail or track from its designed alignment. |
| MSP | Measured Shovel Packing |
| MSS | Maximum Safe Speed |
| NEW TRACKBED | Trackbed layers placed where there was previously no track. Compare with ‘Renewal (of trackbed)’. |
| NON-BALLASTED TRACK | Track that is not supported on ballast, including concrete slab track, track supported on longitudinal timbers and directly fastened track on bridges. |
| NORMAL AND REVERSE | The 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. |
| NSKT | No Signaller - Key Token |
| NSSL | Neutral Section Switching Location |
| NSTR | No Signaller - Token Remote |
| OBTUSE CROSSING | An assembly to permit the passage of wheel flanges where two rails intersect at an obtuse angle. |
| 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 carries |
| OCCUPATION CROSSING | Level crossing, which does not carry a public road, but one which leads to a farm, factory, etc. |
| OLE | Overhead 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 |
| OUTAGE | An 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. |
| OUTFALL | Place at which one-drainage system discharges into another drainage system or watercourse |
| OVERSPEED | The amount by which the actual speed of a train could exceed the enhanced permissible speed for any reason. |
| PANTOGRAPH | On train equipment for collecting electricity from overhead power cable |
| PEE-WEE | A warning device for use by personnel on or near the line |
| PERMANENT WAY | The track structure, which includes rails, sleepers and ballast; any blanketing material (including geotextiles) and associated drainage (also known as P-Way) |
| 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), track ballast and sub-ballast material or drainage |
| PERMISSIBLE SPEED | The 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 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 |
| PETS | Public Emergency Telephone System |
| 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 |
| PLAIN LINE | Track not incorporating switches and crossings. The term ‘plain line’ therefore excludes the through route of S&C. |
| PLB | Possession Limit Board |
| PLGS | Position Light Ground Signal |
| PLJI | Position Light Junction Indicator |
| PLOD | Patrolman's Lockout Device (trackside staff protection system) |
| PLS | Position Light Signal |
| POINT END | An 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 MOTOR | A device used to move the points blades |
| POINT OPERATING MECHANISM | Equipment provided to drive a point end between the normal and reverse positions, using powered or mechanical means. |
| 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 |
| POSSESSION | A 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 |
| PPE | Personal Protective Equipment |
| PRIMARY DRIVE | The point operating mechanism positioned at the toe of points. |
| PROPELLING | Moving a train using a locomotive at its rear |
| PROTECTION | 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 |
| PSB | Power Signal Box |
| PTS | Personal Track Safety: in relation to the Personal Track Safety Certificate |
| PUSH-PULL | A 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-TRAINS | Trains with British Transport Police onboard to combat trespass and vandalism |
| R/G | Miniature red/green warning lights (at level crossing) |
| 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 |
| RAILHEAD | Running surface of the rail |
| RATE OF CHANGE OF CANT | The rate at which a vehicle experiences the change in design cant measured in millimetres per second. |
| RATE OF CHANGE OF CANT DEFICIENCY | The rate at which a vehicle experiences the change in design cant deficiency measured in millimetres per second. |
| REACTIONARY DELAY | The delay to trains resulting from an earlier train delay |
| 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 in safety |
| REGULATE | Signallers 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 CURVE | Two abutting curves of opposite flexure or hand. |
| ROAD | Railway jargon for railway line |
| ROLLING CONTACT FATIGUE | On or just below the running surface of a rail caused by the interaction of steel wheels on steel rails |
| 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. |
| RUNNING ROUND | Transferring a locomotive from one end of a train to the other by means of a loop |
| S&C | Switches and Crossings: the specially machined rails designed to permit trains to transfer between tracks |
| S&C LAYOUT | A 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 UNIT | Half 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&T | Signalling and Telecommunications |
| 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 |
| SANDITE | Mixture of sand and antifreeze, used for assisting traction adhesion during extreme weather. Sandite S4 also contains steel shot to assist track circuit operation |
| SANDITE TRAIN | Train applying a liquid substance with suspended particles of sand to improve adhesion |
| SCOTCH | 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 |
| SCOTCH BLOCK | A device attached to a rail that will, when in its effective position, prevent the movement of stationary vehicles. |
| SECTION SIGNAL | The stop signal, which controls the entrance to the Block Section (or intermediate block section) ahead (often called the “starter”) |
| SEMAPHORE SIGNALS | Signals 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 |
| SENTINEL | Personal Track Safety Identification/Certification System |
| SET | A complete train, including locomotive and carriages, or a multiple unit train |
| SHOE | the apparatus by which an electric train picks up current from the third rail |
| SIDE WEAR | The reduction in rail head width due to wear caused by flange contact with the rails as trains run around a curved track |
| SIDEWEAR | The 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 HEADWAY | The minimum interval between trains allowed by the signalling system |
| SIGNAL SIGHTING | The viewing of a signal from a train driver’s perspective |
| SPAD | Signal Passed at Danger |
| SQUAT | A rail specific defect usually visible on the surface of the railhead |
| STABLING | Parking of trains, which are not in use for a period (e.g. overnight) |
| STANDARD DEVIATION | Standard 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. |
| STRESSING | The 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 DRIVE | A 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 CROSSING | A 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 DIAMONDS | A 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 RAIL | The moving portion of rail on each side of a set of points |
| SWITCH TOE | The end of the switch rail that is traversed first by a vehicle negotiating the switch in the facing direction. |
| SWITCHES | A 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 OVALE | A rail fault consisting of a void within the rail, with nothing visible on the exterior. It can be detected with ultrasonic scanning equipment |
| 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 tail lamp he must stop the train |
| TAMPING | A process that compacts ballast under sleepers (see also Regulate) to maintain the correct geometry of the track |
| TCAID | 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 |
| TEN FOOT | Identifies the central space on a four track railway (may actually be less than six feet) |
| THIRD RAIL | An 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 LIPPING | The 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 |
| TPWS | Train Protection Warning System |
| TPWS+ | TPWS functionality at higher speed |
| TRACK CIRCUIT | An electrical device using the rails in an electric circuit, which detects the absence of trains on a defined section of line |
| TRAILING POINTS | Where lines converge in the direction of travel (also see Facing Points) |
| TRAIN DESCRIBER | The 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 CURVE | The designed parabolic curve linking a straight rail 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 the adhesion between wheel and rail |
| 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 |
| UP LINE | Track with a normal direction of running generally towards London |
| WETBEDS | Deterioration of sleepers and ballast caused by saturation |
| WHISTLE BOARD | A line sideboard, which indicates to train drivers where they are required to sound a warning |
Skip to content