0–9

A

Adhesion railwayThe most common type of railway, where power is applied by driving some or all of the wheels of the locomotive^[2]Adhesive weightThe weight on the driving wheels of a locomotive, which determines the frictional grip between wheels and rail, and hence the drawbar pull a locomotive can exert^[3]Air brakeA power braking system withcompressed airas the operating medium^[4]Alerter or watchdogSimilar to thedead man's switchother than it does not require the operator's constant interaction. Instead, an alarm is sounded at a preset interval in which the operator must respond by pressing a button to reset the alarm and timer if no other controls are operated. If the operator does not respond within a preset time, the prime mover is automatically throttled back to idle and the brakes are automatically applied.^[5]All weather adhesionThe adhesion available during traction mode with 99% reliability in all weather conditions^[6]AlternatorAnelectrical generatorthat converts mechanical energy to electrical energy in the form ofalternating current^[7]American Locomotive Company(ALCO)The second largest builder of steam locomotives in the United States^[8][9]American typeA steam locomotive with a4-4-0wheel arrangement^[10]Angle cockA valve affixed to each end of a piece of rolling stock that, when opened, admits compressed air to the brake pipe (or vents it to the atmosphere if air hose is detached)^[11]Articulated locomotiveA steam locomotive with one or more engine units that can move relative to the main frame^[8][12]ArticulationThe sharing of one truck by adjacent ends of two rail vehiclesAshpanA feature of a locomotive with the same form and purpose as the domestic variety (i.e., to collect the ashes that fall through the bars of the grate). The only significant difference is the size, measured in feet rather than inches.AsynchronousAn alternating current electric motor whose speed varies with load and has no fixed relation to the frequency of the supplyAtlantic typeA steam locomotive with a4-4-2wheel arrangement^[13][14][15]Automatic block signaling(ABS)A system that consists of a series of signals that divide a railway line into a series of blocks and then functions to control the movement of trains between them through automatic signalsAutomatic train control(ATC)A system that applies an emergency brake if the driver does not react to certain signals or speed restrictions^[16]Automatic train operation(ATO)An operational safety enhancement device used to help automate operations of trainsAutomatic train protection(ATP)A system that enforces obedience to signals and speed restrictions by speed supervision, including automatic stop at signals^[17]AutotrainAbranch-linetrain consisting of a steam locomotive and passenger carriages that can be driven from either end by means of rodding to theregulatorand an additionalvacuum brakevalve. The fireman remains with the locomotive and, when the driver is at the other end, the fireman controls thecut offand vacuum ejectors in addition to his usual duties. See also:Push-pull train.Axleboxor axle boxThe housing that holds the axle bearings on a rail vehicle^[18]The housing that attaches to the end of the axle to the bogie and contains the bearing on which the axle rotates^[19] See also *journal box

• below.

B

BackheadThe cab-side rear panel of a steam locomotive boiler through which the firebox is accessed.^[20]Bad orderA tag or note applied to a defective piece of equipment. Generally, equipment tagged as bad order must not be used until repaired, inspected, and approved for use.^[21][22]Bail offTo release the locomotive brakes while the train brakes are applied, to permit smoother handling and prevent excessive slack,wheel slideandflat wheels^[23]BalancingThe reciprocation and revolving masses of any steam, diesel or electric locomotive need balancing, if it is to work smoothly. Revolving masses can easily be balanced by counterweights, but the balancing of reciprocating parts is a matter of compromise and judgement.BaliseA transponder that is used as a intermittent data point in anautomatic train protection(ATP) system or as reference point for train location inradio-based train control^[17]BallastAggregate stone, gravel, or cinders forming the track bed on which sleepers (ties) andtrackare laid to ensure stability and proper drainage^[21][24]Ballast tamperSee *Tamping machine*.BalloonA looped length of track, usually at the end of a spur or branch, which trains use to turn around for the return trip without reversing or shunting. Can be used as part of a freight installation to allow the loading or unloading of bulk materials without the need to stop the train (seemerry-go-round train(MGR)).Bay platformAplatformand track arrangement where the train pulls into a siding, or dead-end, when serving the platformBeepA one-of-a-kind switcher *locomotive

• (also referred to as the SWBLW) built by the

Atchison, Topeka and Santa Fe Railwayin 1970BellmouthA widening of an underground rail tunnel, in preparation for future connection or expansion of service. Used particularly insubwaynomenclature.^[25][26]Berkshire typeA steam locomotive with a2-8-4wheel arrangement^[27][28][29]BlastpipeA part of a steam locomotive that discharges exhaust steam from the cylinders into the smokebox beneath the chimney to increase draught through the fireBlock sectionA section of track in a fixed block system that a train may only enter when it is not occupied by other vehicles^[30]Bo-Bo(Europe)A locomotive with a four-wheel per truck configuration, each individually powered, as opposed to a six-wheel "Co-Co" configurationBogieA swivel-mounted wheel assembly.BoilerA cylindrical container adjacent to the firebox in which steam is produced to drive a steam locomotive^[31]BolsterA transverse floating beam member of a truck suspension system supporting the weight of a vehicle body^[32]Boom barrierA pivoted road barrier at alevel crossingBooster engineAn extra set of cylinders that can be engaged on a steam locomotive to drive atrailing truckor tender truck to give additional tractive effort at starting and low speeds^[21][33]Brakeman's cabinor brakeman's cabA small hut at one end of a railway wagon to protect the brakeman from the elementsBrake pipeThe main air pipe of a train'sair brakesystem^[34]Branch lineA secondary railway line that splits off from a main line^[21]Brick archA brick or concrete baffle provided at the front of a locomotive firebox below the tubes to extend the flame path. Early locomotives burned coke; provision of a brick arch was necessary before coal could be used without producing excessive smoke.British Rail Universal Trolley Equipment(BRUTE)A type of platform trolley found on stations all over the UK rail network from the late 1960s to the early 1980sBroad gaugeTrack where the rails are spaced farther apart thanstandard gauge, or1,435 mm(4 ft 8¹⁄₂ in)^[21]Bubble carA nickname for aBritish Rail Class 121railcar^[35]Buckeye couplerA side-operated version of the top- or bottom-operatedJanney coupler^[36]BufferA device that cushions the ends of rail vehicles against each otherBuffer stopor bumper postThe barrier installed at the end of a dead-end track to prevent rail vehicles from proceeding furtherBuilder's plateThenameplatefitted by their manufacturer to locomotives and items of rolling stockBulkhead flatcarAn open-topflatcarwith a wall at each endBungalowThe housing for signals and communications computers that control switches, crossings, and other such controls, relaying information to and from the rail traffic control (RTC)^[37]BustitutionAportmanteauof the words "bus" and "substitution", the practice of replacing a train service with one provided by buses, whether as a temporary or a permanent measure

C

CabThe control room of a locomotive housing the engine crew and their control consoles^[38][39]Cab forwardA steam locomotive with its cab at the leading end of the boiler, rather than the usual trailing end adjacent to the tender. The best known example is theSouthern Pacific Railroad's AC type, built to handle drag freights through the SP's many tunnels and snow sheds without the danger of the exhaust asphyxiating the engine crew.CablessA locomotive without a cab. Commonly referred to as a *B unit

• or a *

Slug*, although not all Slugs are cabless.CabooseA railroad car attached usually to the end of a train, in which railroad workers could ride and monitor track and rolling stock conditions. Largely obsolete, having been replaced by the electronicend-of-train device(ETD), or flashing rear-end device (FRED).^[40]CantThe angle of an individual rail relative to vertical (e.g., around curves)Carbody unitA locomotive that derives structural strength from a bridge-truss design framework in the sides and roof, which cover the full width of the locomotiveCatenaryThe overhead wire system used to send electricity to anelectric locomotiveormultiple unit, tram or light rail vehicle^[40]CenterbeamA bulkhead flatcar with a braced beam bisecting its length, used to transport lumber productsChallenger typeA steam locomotive with a4-6-6-4wheel arrangement^{[41][42][43][44]}ChordA section of subsidiary track that interconnects two primary tracks that cross atseparated grades, to permit traffic to flow between them.Co-Co locomotives(EU)A heavier duty locomotive with sixwheelsper bogie (all axles being separately driven) configuration as opposed to a four-wheel "Bo-Bo" configuration. The correct classification is Co'Co', but Co-Co is used more often.Coal pusherA steam-operated device in the tender intended to push coal forward to a point where it can be shovelled directly into the fire^[45]Colour light signalA signal in which the colour of the light determines the signal meaningColour position signalA signal that uses both colour and light position to indicate meaningCombined power handleA handle orleverthat controls both thethrottleanddynamic brakingon the locomotive: on a desktop-type control stand, forward (away from operator) past center operates the dynamic brake, backward (toward operator) past center, is throttle up^[46][47][48]Compound locomotiveA steam locomotive passing steam through two sets of cylinders. One set uses high pressure steam, then passes the low pressure exhausted steam to the second.^[49]Configurable SystemCapability of the system to allow users to select, from pre-programmed functions (modular software units), those functions necessary to accomplish a control strategy or other complex function, without the use of computer language^[50]ConsistSingle vehicle or a group of vehicles that are not separated during normal operation^[51]Consolidation typeA steam locomotive with a2-8-0wheel arrangement^[52][53]Container on flat car (COFC)The loading of a shipping container onto a simple flat car^[40]Continuous welded rail(CWR)A form of track made from railsweldedtogether by with athermitereaction or flash butt welding to form one continuous rail that may be several kilometres long^[40]Control carA passenger coach with a full set of train controls at one end, allowing for the use ofpush-pulltrain operation^[54]Control SystemThe microprocessor based control and fault diagnostic system has been developed for conventional electric locomotives including locos provided with static converter. It performs logical control of the locomotive by continuously monitoring various digital/ analog inputs and checks for any abnormality in the operation.^[55]Coupler pulling faces, length overEffective length of piece of rolling stockCoupling rodsRods between crank pins on the wheels, transferring power from a driving axle to a driven axle of a locomotive^[56]Covered goods wagon(UIC)A type of rolling stock with a flat bottom enclosed on all sides and top, which is loaded and unloaded from sliding doors on each side^[21][57]Cow-calfor cow and calfA diesel locomotive with a crew cab permanently coupled to and acting as a controller for a similar slave diesel locomotive without a crew cab, primarily used for switching or shunting duties for large groups of rolling stock. Also known as master and slave.Crank pinA pin protruding from a wheel into a main or coupling rodCrossheadIn a steam locomotive, the moving member of a sliding guide that absorbs upward and downward forces from the connecting (main) rod, which otherwise would tend to bend the piston rod^[58]CutTo uncouple one or more cars from a train (i.e. to "make a cut")^[59]Same as "cutting"^[59]Cut leverA manual lever that releases the pin of anautomatic couplerwhen pulled to separate cars or locomotives^[60][61]Cut offA variable device onsteam locomotivesthat closes the steam valve to thesteam cylinderbefore the end of the piston stroke, thus conserving steam while letting steam in the cylinder expand under its own energy. See also:Reverser handle.CuttingA channel dug through a hillside to enable rail track to maintain a shallow gradient. See also *embankment*.Cycle brakingMaking repeatedservice brakereductions in short succession to maintain a constant speed on short but steep grades. Each reduction must be at least 5 PSI lower than the previous one to keep the brakes applying regularly, but excessive cycle braking can deplete the air supply and require an emergency application.^[62]CylinderA cavity in a reciprocating engine in which a piston travelsCylinder cockOn steam locomotives, crews use this appurtenance to drain water from the steam cylinders when the throttle is open, thus preventing damage to the pistons, running gear, and cylinder heads^[63]

D

Dark signalAblock signalthat is displaying no discernible aspect, often due to burned out lamps or local power failure. Most railroads require that a dark signal be treated as displaying its most restrictive aspect (e.g. stop and stay for anabsolute signal).^[64]Dark territoryA section of track withoutblock signals^[65]Dead man's handleA safety mechanism on a train controller that automatically applies the brake if the driver releases the handle. It is intended to stop a train if the driver is incapacitated. In some forms, this device may be pedal-actuated. See alsoDead-man's vigilance device.Decapod typeA steam locomotive with a2-10-0wheel arrangement^[66][67][68]Defect detectorA track side device used to detect various defects such ashotboxes(overheated axle bearings), dragging equipment, leaning cars, overloaded cars, overheight cars, seized (locked) wheels, etc.^[69]Degraded OperationOperation resulting from an unplanned event that prevents the normal delivery of train services^[70]DemurrageA monetary charge levied by a railroad to a customer for excessive delay in loading or unloading carsDerailor derailerA safety device that derails vehicles that pass it, typically to prevent rolling stock from accidentally entering themainlinefrom a siding^[69]DetonatorA small explosive charge placed on the running rail, which detonates loudly when run over to warn drivers in following trains of an incident ahead. Known as atorpedoin the United States.DiamondTrack that lets a rail line cross another at grade^[69]Diesel multiple unit(DMU)A set of diesel-powered self-propelling passenger rail vehicles able to operate in multiple with other such sets. Such units, especially those consisting of a single vehicle, are sometimes termedrailcars.Direct traffic control(DTC)A system in whichtrain dispatcherscommunicate directly with train crews via radio to authorize track occupancy in predefined blocks^[69]Distributed powerA practice employed to move large trains through the mountains. Consists of the locomotives on the head end, a "swing" (mid-train) helper or two, and pusher locomotive(s) on the rear; today, all units are remotely controlled by the engineer in the lead unit. The power distribution alleviates stress on the couplers and relieves the lead units of the full weight of the train, making it easier to move on grades.Ditch lightsA pair of lights, usually found on modern locomotives, located some distance below and outboard of the main headlight. They may also flash alternately when a locomotive sounds itshorn^[71]DivisionThe trackage area under the jurisdiction of a railway superintendent^[72]Dog or dogspike (India)Aspikewith a slightly altered head shape for easier extraction when the spike has become too loose in the sleeper^[73][74]DoodlebugA self-powered gasoline-electric passenger car used for small capacity rural commuter service.^[69] Also aBritish Rail Class 153DMU.DoubleIf a train has insufficient power to climb a grade and no helpers are available, the crew splits the train into two sections and runs them separately to the top.^[75]Double headingA configuration in which two locomotives are coupled head-to-tail so they can haul a heavy train up a long or steep hill. Currently, double heading (and occasionally triple heading) are used primarily by large passenger trains or as a show for railfans.DragA long, heavy freight train moving at low speedDragging equipment detectorSeeDefect detector.^[69]DrawbarThe part of a coupler that attaches to the frame of the car or locomotive; may be equipped with a pneumatic cushion depending on a freight car's design cargo (e.g. anautorack). Alternately, the pinned double bars coupling a steam locomotive to its tender.Driver or engine driverThe operator of a locomotive^[76]Driver only operation (DO or DOO)Operation of a train by theengineeror driver only.^[77] Also known asone person train operation(OPTO)DriverA wheel in contact with the rail that also propels a locomotiveDwarf signalA signal light that is considerably smaller and closer to the ground than a high-mast signal; often absolute, and placed within interlocking limits, its aspects tend to differ from those conveyed by a taller signal for certain indications. Also called 'pot' or 'jack'.Dwell timeThe time a train spends at a scheduled stop without moving. Typically, this time is spent boarding or deboarding passengers, but it may also be spent waiting for traffic ahead to clear, or idling time in order to get back on schedule.^[78]Dynamic brakingThe use of a traction motors' output, working as generators, to retard train speed without relying solely on the air brakes

E

EjectorA component ofvacuum brakesystem usually fitted in pairs. Steam passing through a cone sucks air from the train pipe to create the vacuum.A small ejector running continuously to overcome leaks and to restore the vacuum after light braking and a large ejector operated when needed to release the brakes quickly after a heavy application or to create the initial vacuum after couplingElectric multiple unit(EMU)A set of electrically powered self-propelling passenger rail vehicles able to operate in multiple with other such setsElectro-Motive Diesel(EMD)The world's second largest builder of railroad locomotives. EMD was previously Electro-Motive Division ofGeneral Motorsbefore being sold.Elevated railway, el, or LA railway built on supports over city streetsEmbankmentA bank, usually of earth but sometimes of stone, constructed to form a level or minimally gradedtrackbedfor a line of railway needing to pass over a depression in the terrain or other pre-existing surface feature. See also cutting.Empty coaching stock (ECS)A train used to bringcarriagesinto (or out of) service. They usually run betweensidingsand mainstations, with the carriages then forming a service train to another destination. They are often worked under freight train rules (e.g. without needing a guard in the UK).^[79]Emergency releaseA device accessible under certain conditions that permits the operation of an apparatus in case of failure^[80]End-cab switcherA switching locomotive with no short hood, thus having its cab forming one end of its car bodyEqualizing reservoirA small air reservoir in a locomotive control stand. When the automatic brake valve is operated, this reservoir responds by reducing or increasing the air pressure in the brake pipe.^[81]Event recorderA device that continuously captures analog and digital train systems information and stores that data for a minimum of 48 hours. This data is used to evaluate incidents and accidents. Typical stored data includes speed, brake pressure, dynamic brake, horn activation, track signal, etc. In the U.S., event recorders are mandated by the Federal Railroad Administration (FRA) for freight, passenger and commuter rail. Regulations for railroad outside the U.S. vary by country. Transit operations are not generally required to have event recorders, but have begun to add them voluntarily.Express trainA train that passes selected stations without stoppingExtraA train not included in the normal schedule of a railroad.^[82][83][84] They often run during busy holiday travel periods in order to handle larger crowds and reduce the number of passengers waiting or stranded at a station. Intrain orderterritory, extras are required to clear the main line for scheduled trains to pass.^[85]

F

FacingA turnout that can select which way to diverge a train—the opposite of trailingFairlieA type ofarticulated locomotive, typically (but not exclusively) with twoboilersand connectedfireboxesin a central cabFall plateA heavy, hinged steel plate attached in a horizontal position to the rear of the locomotivefootplateor front of a locomotive tender. When the tender is attached to its locomotive the plate is allowed to fall to cover the gap in the "floor" between the two units. The sliding edge is not fixed and has a smoothchamferso as to avoid a trip hazard.^[86]Fallen flagA defunct railroad.Feedwater heaterA device to preheat the water for a steam locomotive to improve efficiencyFeed valve or regulating valveA valve that controls the amount of air pressure channelled from the locomotive's main reservoir to the brake pipe, in accordance with the set pressure in the equalizing reservoir^[87]Fiddle yardInrailway modelling, a concealed group of sidings used to provide more realistic operation in a limited spaceFireboxIn steam locomotives, a chamber in which a fire produces sufficient heat to create steam once the hot gases created there are carried into the adjacent boiler via tubes or flues^[88]Fireman, stoker, or boilermanA worker whose primary job is to shovel coal into the firebox and ensure that the boiler maintains sufficient steam pressureFlatA wheel defect where the tread of a wheel has a flat spot and is no longer round; flats can be heard as regular clicking or banging noises when the wheel passes by. This is caused either by a locked bearing, or a brake that was not fully released before the car was moved, dragging the wheel without turning.^[89]Flying junctionor flyoverA railway junction that has a track configuration in which merging or crossing railroad lines provide track connections with each other without requiring trains to cross in front of opposing traffic on the same level^[89]Fouling pointA point of a switch turnout where a car or locomotive on one track obstructs movements on the adjacent track^[90]Four-quadrant gateA type ofboom barrierFree-moA type of modular layout in model railroadingFreight wagon(UIC)A rail vehicle designed for the carriage of freightFull service reductionThe maximum air pressure that can be exerted against brake pistons in a normal brake application. To increase pressure beyond this point, the brakes must be placed in emergency.^[91]FuseeA pyrotechnic device similar to an automotive flare that is used in signalling^[89]Fusible plugA threaded plug, with a soft metal core, that is screwed into the crown plate of afirebox. If the water level gets too low the core melts and the noise of the escaping steam warns the enginemen.

G

GarrattA type ofsteam locomotivethat isarticulatedinto three parts^[92]GaugeThe width between the inner faces of the railsGeepAny of the GP ("general-purpose") series ofElectro-Motivefour-axle diesel locomotives; originally applied only toEMD GP7,GP9, andGP18models^[93]Generator fieldThe control switch of a diesel-electric locomotive that opens or closes the circuit between the main generator and the traction motors^[94]Get a knuckleTo break a train in two, usually by shearing the knuckle pin in acoupler, often caused by the application of excessive head end power at startup^[95][96]GEVOA nickname forGeneral Electric'sEvolution seriesof modern diesel locomotives^[97][98]Gladhand connectorA quick coupling and uncoupling connector at the end of a trainline air hose that resembles a pair of shaking hands when hoses are connectedGo-devilA hand-powered railroad car (seeHandcarandDraisine), or a small gasoline powered railroad car^[99][100]Grab bar or grab ironA handle on the side of a car to allow switching personnel to hold on^[101]

H

Harmonic rock or harmonic rock and rollThe condition of locomotives and cars swaying in opposite directions when traversing depressions on the roadbed. A potentially dangerous condition that can cause coupler damage, lading damage, or derailments at slower speeds.^[102][103]A scheme whereby the locomotive engine or a separate generator provides hotel power to carriages^[104]HeadboardA sign attached to a locomotive to identify a named train or charter, or for other special occasions^[105]HeadstockA transverse structural member located at the extreme end of a rail vehicle'sunderframe. The headstock supports thecouplingat that end of the vehicle, and may also supportbuffers, in which case it may also be known as a "buffer beam".^[106]Heavy haulHeavy freight operations^{[107][108][109]}High railThe upper rail in a curve or superelevation, which typically experiences higher lateral loads and greater wearHoleA passing siding. Inferior trains "lay over in the hole" to let superior ones pass.^[110]Home signalSeeabsolute signal.Horn blocksPlates lining the axlebox cut-outs in a locomotive frame to allow smooth vertical movement under control of the springs^[111][112]HostlingThe action of shuttling a locomotive from the yard to the engine house or vice versa^[113]HotboxAn axle bearing that has become excessively hot due tofriction^{[104][114][115]}Hotbox detectorA device attached to the track that monitors passing trains for hot axles, and reports results via radio transmission (typical in the US) or a circuit to the signal box (typical in the UK). See *defect detector*.^[104]Hudson typeA steam locomotive with a4-6-4wheel arrangement^[29][116]HumpA raised section in a rail sorting yard that allows operators to use gravity to move freight railcars into the proper position within the yard when making up trains of cars. This is faster and requires less effort than moving cars with a switching engine.^[104]HuntingSwaying motion of a railway vehicle or bogie caused by the coning action on which the directional stability of an adhesion railway depends. The truck or bogie wanders from side to side between the rails, "hunting" for the optimum location based on the forces at play.^[104]

I

Independent brake or locomotive brakeThe braking system that applies or releases the brakes of a locomotive independently from its train^[117][118]Infill stationor in-fill stationAtrain stationbuilt on an existing passenger line to address demand in a location between existing stationsInjectorA device to force water into a steam locomotive's boiler by steam pressure^[119]Insulated rail joint (IRJ) or insulated block joint (IBJ)Rail joints incorporating insulation to isolate individual track circuits^[120][121]InterchangeAny track or yard where rail cars are transferred from one carrier to another^[122][123]InterlockingAn arrangement of switches and signals interconnected in a way that each movement follows the other in a proper and safe sequence^[124]Intermodal freight transportMoving goods by more than one type of vehicle, often achieved using shipping containers that are transferred among railroad flatcars, ships, airplanes, and tractor-trailer trucks^[119]Intermodal passenger transportMoving people by more than one type of vehicle^[119]InteroperabilityAbility of a transport network to operate trains and infrastructures to provide, accept and use services so exchanged without any substantial change in functionality or performance^[125]Island platformArailway platformthat has tracks along the full lengths of both sides

J

Jacobs BogieABogie, or truck (American), shared between two pieces of rolling stock. Cars joined with Jacobs bogies are semi-permanently joined in anarticulatedconfiguration. A weight-saving feature used on lightweight passenger trains.Joint bar or rail joinerA metal plate that joins the ends of rails in jointed track^[126]Jointed trackTrack in which the rails are laid in lengths of around 20 m and bolted to each other end-to-end by means of fishplates or joint bars^[127]Journal bearingA bearing withoutrolling elements; a plain bearing^[128]Journal boxThe housing of a journal bearing.^[128][129] See alsoAxleboxabove.Jubilee typeA steam locomotive with a4-4-4wheel arrangement^[130]JunctionA point at which two lines or separate routes diverge from each other^[127]

K

KeeperA padlock or hook securing the lever of a hand-operated switch, thereby preventing the switch points from moving as rolling stock passes over them^[131][132]KickTo shove a car a short distance and uncouple it in motion, allowing it to roll free under gravity and/or its own inertia onto a track. Commonly practiced in bowl orhump yardsto make up or break down trains or classify large numbers of cars in an expedient fashion. Differs from aflying switchin that the locomotive is pushing the car rather than pulling it when the cut is made.^[133]KickerA freight car with a defect in its brake valve that causes the entire train's brake system to go into emergency when any application is made^[134]Kinematic envelope (KE)The outline of the space beside and above the track that must be keptclearof obstructions for the train to pass. This can be larger than the static clearance around an unmoving engine or car.^[135] See also:loading gaugeandstructure gaugeKnuckleThe articulating part of a coupler that locks automatically in its closed position to join rail cars; so named because its movement resembles that of the human finger^[136]

L

Lead trackA non-main track from which several others branch within a short distance, such as within arail yardor engine terminal^[137]Level crossing, railroad crossing, railway crossing, train crossing, or grade crossingA crossing on one level ("at-grade intersection")—without recourse to a bridge or tunnel—generally of a railway line by a road or pathLight engineA locomotive travelling on its own, or perhaps with just a caboose (brake van) attached^[138]Light railA city-based rail system based ontramdesign standards that operates mostly inprivate rights-of-wayseparated from other traffic but sometimes, if necessary, mixed with other traffic in city streets.^[139] Light rail vehicles (LRVs) generally have a top speed of around 55 mph (89 km/h) though mostly operating at much lower speeds, more akin toroad vehicles. Light rail vehicles usually run on trackage that weighs less per foot (due to a smaller track profile) than the tracks used for main-line freight trains; thus they are "light rail" due to the smaller rails usually used.^[138]Link and pinAn obsolete method of coupling rail cars, consisting of manually dropping the coupling pin into the drawbar as the cars joined. Extremely hazardous to the brakemen of its day, it was outlawed in the United States by theRailroad Safety Appliance Actof 1893.Local trainA train that stops at most, if not all, stations along its route^[140]LunarAn off-white color ofrailway signallight, like theMoon, achieved by the use of a clear lens of very light blue, to make it distinct from a light that has a broken lens.^[141][142]

M

Main generatorTheelectric generatorin a diesel-electric locomotive that is coupled directly to theprime moverand feeds electrical energy to the traction motors^[143]Main reservoirThe compressed-air tank of a locomotive containing source air for the brakes and other pneumatic appliances^[144]MalletA type ofarticulated locomotivedesigned by the Swiss mechanical engineerAnatole Mallet(pronounced "mallay").^[145][146] SeeCompound engine.ManifestAn express freight train carrying a variety of general merchandise^[147][148]Mars LightA nose-mounted mechanically oscillated light used to warn traffic of an approaching locomotive. Functionally replaced by ditch lights on modern locomotives.Mechanical semaphore signalA signal in which the aspect is conveyed by moving an arm^[149][150]Mikado typeA steam locomotive with a2-8-2wheel arrangement^[151]Milk trainIn the U.S., milk trains ran from the countryside to cities making numerous stops at minor depots to pick up cans of fresh milk, making them a colloquial expression for a very slow train.In the U. K., an aggregator for transporting milk from farms to dairies, such asBritish Railways Milk Trains^{[152][153][154]}ModalohrAn inter-modal carMogul typeA steam locomotive with a2-6-0wheel arrangement^[155]MothballedA track that is still serviceable but no trains are running on them.^[156][157]Mountain typeA steam locomotive with a4-8-2wheel arrangement^[158]Mud ringThe bottom of the water space surrounding a steam locomotive's firebox that collects solid deposits distilled from the water supply during the boiling process^[159]Multiple aspect signallingA system of colour-light signalling in which signals may show three or four aspects^[160]Multiple unit(MU)A self-propelled rail vehicle that can be joined with compatible others and controlled from a single driving station. The sub-classes of this type of vehicle;Diesel Multiple Unit(DMU),Diesel-Electric Multiple Unit(DEMU) andElectric Multiple Unit(EMU) are more common terms. These may also be termedrailcars.

N

Narrow gaugeRailroad track where the rails are spaced less than1,435 mm(4 ft 8¹⁄₂ in) apart,^[161]Northern typeA steam locomotive with a4-8-4wheel arrangement, also known in North America as "Pocono", "Niagara", "Confederation", "Greenbrier", and "Potomac"^[162][163]Notch 8or run 8The eighth notch of a locomotive throttle control, indicating full power^[164][165]

O

Open wagon(UIC)A form of freight hauling car for bulk goods^[166]Out to foulWhen equipment is placed ahead of the fouling point of a switch turnout

P

Pacific typeA steam locomotive with a4-6-2wheel arrangement^[167]Pannier tankAtank locomotivewhere the water tanks are mounted on the boiler inpannier-like fashionPantographAn apparatus mounted on the roof of a rail vehicle to allow the collection of electric current fromoverhead lines^[168][169]PaperworkAs a reason for delays, written instructions conveyed to a train's engineer in which the train must proceed slower than its normal speed. These instructions are either handed to the crew or recited and read back over radio.^[170]PennsyAbbreviation for the formerPennsylvania Railroad^[171]Per diem(pronounced by some U.S. railroaders per die-um, not per dee-um)A fee paid by a rail company to the owner of a car (or wagon) for the time it spends on the company's property^[168][172]An authorized living expense payment for some workers forced away from their home terminal^[168][173]Permissive signalAblock signalwhose most restrictive indication is stop and proceed. A permissive signal is identified by the presence of a number plate affixed to the mast or supporting structure. Proceeding beyond a permissive signal at stop is allowed at restricted speed if operating conditions enable a train operator to stop before reaching any train or obstruction.^{[174][175][176]}PilotA deflective shield affixed to the front of a locomotive to protect its wheels from on-track debris; archaically called a "cowcatcher"^[177] See also:Pilot (locomotive)An employee qualified on the operating rules and physical characteristics of a certain section of the railroad, assisting a crew member who is not so qualified^[178][179] See also:Railroad engineerPilot engineThe leading locomotive during adouble-headingoperation^[180]An unattached locomotive driven a specified distance in front of a special train^{[180][181][182]}Pilot manWhere it is necessary to temporarily work a section of line as single track (for instance if the other track of a double-track line is out of use), a person (the pilot man) acts as the single tracktoken.PistonThe moving component in thecylinderof asteam engineorinternal combustion enginethat translates into motion the force exerted by pressurised steam or quickly-burning fuel^[183]Piston travelA specified distance that a brake piston may move from its cylinder to the brake rigging. If the travel exceeds or falls short of this distance, the equipment must be set out for repair.^[184]Pony truckA two-wheel truck or bogie at the front of a locomotive^[185]PorchThe extended walkway at either end of a U.S. locomotive^[186]PorterAn employee who performs or performed (the role has now largely become obsolete) various physical duties, chiefly but not exclusively involving lifting. Various types of porter include:

• A baggage porter assisting with luggage
• An operating porter assisting withsafeworkingduties
• A station porter assisting with general station duties
• A lad porter being a junior station porter

Portion workingThe practice of coupling two or more passenger trains together over common sections of their respective routes, but otherwise operating the trains separately^[187][188]Position light signalAblock signalin which the relative position of the lights determines the meaningPositive train control(PTC)A system of functional requirements for monitoring and controlling train movements with the aim of increasing operational safetyPossessionA period of time when one or more tracks are closed for maintenance. For the duration of the work, a person in charge of possession (PICOP) has control of the line. When work is complete the possession is relinquished and control of the line handed back to thesignaller.^[189]PoundThe weight (and thus the cross section) of a length of rail. A heavier rail can carry heavier loads with less distortion and less damage to the rails themselves and the roadbed.PowerA locomotive or group of connected (MU'd) locomotives serving as the motive power for a train^[168]Power brakingPulling against the train brakes at the higher end of the locomotive's power output (e.g. notches five through eight on a conventional throttle). This is considered wasteful of fuel and brake shoes, and is therefore discouraged by most operating departments.^[190][191]Prairie typeA steam locomotive with a2-6-2wheel arrangement^[192]Prime moverThe internal combustion engine of a diesel locomotivePull apartA rail broken from cold-related contraction^[193][194]Push poleA pole about 12 feet (366 cm) long and having a diameter of 5 inches (127 mm) and used in the United States between 1870 and the mid-1960s to push a freight car onto or off a siding or onto another track by being placed between a locomotive (on an adjacent track) and the freight car. The two ends of the poles were placed in receptacles called push pole pockets.^[195]Push–pull trainA configuration for locomotive-hauled trains, allowing them to be driven from either end of the train, whether having a locomotive at each end or not. See also:Auto train. SeeTop and tailfor train with locomotives at both front and back.^[168]

R

Rack railway, rack-and-pinion railway, or cog railwayA steep-grade railway with a toothed rack rail (usually between the running rails), used when adhesion is insufficientRailbusA passenger rail vehicle (typically non-articulated or rigid frame) that derived from bus propulsion and construction technology, but may evolve into larger dimensions, performance, and characteristics similar in appearance to a lightDMUrailcarRailcarA powered single unit orarticulatedpassenger car, usually “railroad-derived” light DMU orEMU, with a driver's cab at one or both endsRailfanA hobbyist or enthusiast of trainsRail grinderA machine used to remove irregularities in the surface of the rails that may be self-powered or part of aconsistRail profileThe cross section shape of rail. There are many rail profiles, often specific to individual railroads. Rails must be periodically scanned electronically, the data inspected and analysed, then re-profiled with rail grinding machines to maintain the safe and proper rail profile. Rails that cannot be brought back to the proper rail profile are condemned and replaced.Rail squealA screeching train-track friction sound, most commonly occurring onsharp curvesor heavy braking^[196]Rail tractorA small petrol (gas) or dieselshunting(switcher) locomotiveRailroad carAny railroad vehicle other than a locomotiveRailroadianaArtifacts of railways around the worldRailway lineA railway route connecting two or more places or other railway routes^[197]A railway route constructed by an organization, usually one formed for that purpose^{[197][198][199]}A railway route that has an official name (notably bestowed byengineers line referencesin the UK)^[200]A set of railway routes that are bundled for publicity purposes (e.g., a UKtrain operating company)^[201][202]Railway stationAtrain station, a stopping point for trains, usually with passenger accessRailway terminalA building for passengers at the end of a railway lineRedA colour generally associated with stop, when shown by signals or flagsRed zoneThe area between, under, or within a few feet of cars and locomotives. To enter the zone, a ground employee must obtain protection from the locomotive engineer (if a locomotive is coupled) or a blue signal (if no locomotive is coupled).^{[203][204][205]}ReeferA refrigerated railcar, used to transport perishable goods^[206]Refuge sidingA siding used as a passing place on a main line, where slow trains may be held whilst an express passes—a simpler, but less convenient, form of the passing loopReporting markA two- to four-letter code, assigned by theAssociation of American Railroads, that is applied to equipment operating on North American railroads to identify the owner^{[207][208][209]}Rerail frog or rerailerA metal casting slotted over the rail near the wheel of a derailed train car. The engine then pushes or pulls the car so that the derailed wheel runs up the rerailer and back onto the track.^[210]RetarderA device installed in aclassification yardused to reduce the speed offreight carsas they are sorted into consists^[211]Reverserorreverser handleThe handle that controls the directional control on a locomotive. See alsoCut off.Ribbon railContinuously welded rail^[207]Right-side failureA failure in a signalling or other safety critical system that leaves the system in a safe condition^[212]RoadrailerA highway trailer, or semi-trailer, that is specially equipped for direct use on a railroadRolling stockIn UK parlance, any railway vehicle that is not capable of moving under its own power^[213]In US parlance, any railroad car or locomotive^{[207][214][215]}RookieSeeTrainee.RotaryShort forrotary snowplow, an extreme-duty railroad snowplow used mainly in the mountain ranges of the American West^[216]RoundhouseA circular or semi-circular structure used for storage and running maintenance of locomotivesRoute selector panel, punch box, or train-identification pushbuttons (New York City Subway)A box or panel adjacent to a rail line at aninterlocking, with several buttons for train operators to select a desired route, which is then either communicated to a signal tower where an operator fulfills the request, or switched automatically^[217][218]Ruling gradientThe longest or steepest grade on a division, thus setting the standard for track speeds, locomotive tonnage ratings, and train handling instructions^[219]RunThe action verb for the train's movement. The train runs across the track.RunawayA heavy train that has lost speed control while descending a steep grade, due to either brake failure or poor preparation by the crew^[220]Running trackAn other-than-main track, typically providing access to a yard or industry and governed by the requirements of restricted speed^[221]Run-roundThe practice of detaching a locomotive from its train, driving it to the other end of the train and re-attaching it, to allow the train to proceed in the direction it has just come from (e.g. when it reaches its destination and forms a service in the other direction).^[207][222]Run-through powerLocomotives that remain attached to a manifest or unit train from their home rails over the tracks of a receiving railroad until the train reaches its final destination^[223]

S

Saddle tankAtank locomotivewith the water tank mounted on top of the boiler like a saddle^[224]Safe placeAn area within the network of an operator where evacuation of passengers can be performed, depending on current operational conditions, with a minimum of risk to the passengers (e.g. stations, refuges on the line)^[225]SafeworkingThe system of rules and equipment designed to ensure the safe operation of trains^[226]SandboxA container on locomotives and self-propelled multiple units, or trams, that run on tramways and adhesion railways. The container holdssand, which a crew can drop onto the rail to improve rail adhesion under wet, steep, orslippery railconditions. The sandbox and operating mechanism are collectively known as sanding gear.SanditeConsists of a mixture ofsand,aluminium, and a unique type of adhesive, used instead of plainsandfor extremeslippery railconditionsSanta Fe typeA steam locomotive with a2-10-2wheel arrangement, named for theAtchison, Topeka and Santa Fe Railway—the first railroad to use such a configuration^[227][228]Saturated locomotiveA steam locomotive not equipped with a superheater; the steam thus remains at the same temperature as the water in the boiler^[229]ScaleSolid debris distilled from boiling water in a steam locomotive. To prevent corrosion damage from scale build-up, the locomotive must undergo a boiler wash once each operating month.^[230]Schnabel carA specialized type offreight carfor extra heavy and over sized loads where the car is loaded in such a way that the load forms part of the car superstructure^[231]SearchlightA signal with a single light source usually capable of displaying three different colors. An internal mechanism governs the color displayed.^[224]SectionA portion of atrainthat may be operated independently or combined with other sections to operate as a single unit^[232][233]A portion of railway line designated forsignallingor maintenance^[234][235]An interior portion of asleeping carmade up of two double seats during daytime that convert to two double berths during nighttime^[236]Semaphore signalA type of signal that has a moving arm to change the indicationShay locomotiveA type of geared steam locomotive built to the patents of Ephraim Shay^[224]ShuntIn UK and Australian parlance, to make up and divide trains in sidings, to move trains to or from sidings, or to move trains between platforms in a station^[237]Shuttle trainA train, usually a passenger service, that runs back and forth, usually over a relatively short distance, such as between a junction station and abranch-lineterminus.Side tankAtank locomotivewith water tanks mounted each side of the boilerSidingA section of track off the main line. Sidings are often used for storing rolling stock or freight. A siding is also used as a form of rail access for warehouses and other businesses, where the siding often meets up with loading docks at rail car height. In the U.S. the term also covers the British term *loop*. Also, apassing trackin the U.S.SignalA device that indicates the condition of the line ahead to the driver of a trainSignal boxA building or room that houses signal levers (usually in aframe), a control panel or a VDU-based control systemSignal passed at dangerAn event in which a train passes a signal to stop without authorization to do so^[238]SignalmanA person in charge of the signalling at a station or junction, often in a signal boxSlippery railThe condition of fallen leaves or other debris lying on and clinging to a railroad track that could cause train wheel slippage, resulting in premature wheel wear and train delaysSlow orderA local speed restriction below the track's normal speed limit often designated by yellow and green flags. Slow orders can be imposed on a temporary basis to protect, for example,maintenance of wayemployees while sections of track are under repair. Widely used in areas where track is substandard and in need of repair.SlugA locomotive that contains traction motors yet lacks the diesel engine to create its own power, which is instead supplied by a connected mother locomotive^[224]SmokeboxAn enclosed (normally cylindrical) space attached to the end of the boiler opposite the firebox on a steam locomotive (normally the front). Supports the stack; steam pipes to and from the cylinders pass through here; contains theblastpipewhere the exhaust steam is used to provide draft for the fire. Insuperheatedlocomotives, also contains the superheater header and (optionally) a front-end throttle.Snowplow, snow plow, snowplough, or snow ploughA rail service vehicle used for snow removal from train tracks^[239]Snow shedA long shelter erected over a railroad track on the side of a mountain to protect the line from avalanches and drifting^[240]Span bolsterThe beam between twobogiesSpikeA bolt, pin, or nail used to hold rails, or plates connected to the rails (known as tie plates), to sleepers (ties)Spiral easementSeeTrack transition curve. Also known as tangent lead-in.^[224]SpreaderMaintenance of way equipment designed to spread or shape ballast profiles,remove snow, clean and dig ditches as well as trim embankmentsSelf-propelled ultrasonic rail testing (SPURT) (India)A self-propelled rail-defect detector car^[241]Staff and ticketA method of safeworking involving atoken^[224]Standard gaugeA gauge where the rails are spaced1,435 mm(4 ft 8¹⁄₂ in) apart—by far the most common gauge worldwide^[224]Station masterThe person in charge of a stationSteam generatorA device generally used in passenger trains to create steam for heating. The steam generator is usually in the locomotive but may also be located in other cars.^[224]Steam reverserA reversing gear worked by a steam cylinder controlled from the cabSubdivisionThe trackage area within adivisioncovered by a single timetable^[242]SuperchargerA mechanical device that boosts the pressure of engine intake air to above atmospheric level, causing an increase in power. Not to be confused with theblowerused to scavenge the cylinders of a naturally aspiratedtwo-stroke Dieselengine.SuperheaterA device in a steam locomotive that raises the temperature ofsaturated steamsubstantially beyond the boiling point of water, increasing power and efficiency^[224]SurveyTo determine the position of constructed objects, including rail infrastructure, in relation to the earth's surface. This is accomplished by measuring angles and distances based on the principles of triangulation.SurveyorA person assigned to perform survey workSwitchmanA railroad worker responsible for assembling trains and switching railroad cars in a yard

T

Tamping machineGenerally, a locomotive used in track maintenance and equipped with track lifting facilities, and paddles that push ballast beneath a rail track to assure its level and cantTank carA type of rolling stock designed to transport liquid and gaseous commoditiesTeam trackA spur or siding for loading freight, often used by firms not having their own direct rail access^[243]TenderA specialized rail car attached to a steam locomotive to carry its fuel and water supplies, along with tools and flagging equipmentTerminal railroad(or terminal railway)A company in the United States that owns no cars of its own and transports only therailroad carsof other companies around a specific terminal station^[244]Texas typeA steam locomotive with a2-10-4wheel arrangementThird railAn electrified rail that runs along thetracks, giving power to trains. Used mostly in subways andrapid transitsystems.^[243]Through coachA passenger coach that is disconnected from one train and attached to another before continuing on with its journey, thus avoiding the need for passengers themselves to switch trains^[245]Through platformThe standardplatformand track arrangement at a station. The train pulls alongside the platform, arriving from one end of the station, and may pass out the other end of the station by continuing along the same track^[246]Tie plateA plate bolted to sleepers to the rails in placeTrailer on flat car (TOFC)Intermodal freight transport^[243]TokenA physical object given to a locomotive driver to authorize use of a particular stretch of single trackTrack bedor trackbedThe foundation ofrail tracksTrack bulletinA form used by railroad employees that shows the locations ofslow orders,maintenance of waywork locations, and other conditions affecting the track and movement of trainsTrack circuitAn electrical circuit that detects the presence of locomotives or cars (as their wheelsets electrically bond the rails) in a block of track, and provides real-time input to signaling logicTrack transition curveThe gradual application ofsuperelevationand tighter curve radius, calculated with reference to the anticipated line speed and the final curve radius, on the approach to a bend. Also known as the transition spiral and spiral easement.Trackside objectsSeeWayobjects.Traction motorA large electric motor that powers the driving wheels of anelectricordiesel-electriclocomotive^[243]Tractive effortThe pulling or pushingforceexerted by a locomotive or other vehicleTrailingA turnout where both legs merge in the direction of travel—the opposite of facingTrain couplerThe mechanical interface that links vehicles so a driver can operate them together. The coupler can be a purely mechanical device such as a screw coupler or bar coupler. Alternatively the coupler can also incorporate electrical or pneumatic connections.^[247]TrainmanAn employee assigned to train service, such as a conductor, brakeman, or switchmanTrain inaugurationThe automated process of train bus configuration that includes detecting all bus nodes and their orientation, assigning the numbers to particular bus nodes and collecting their properties.^[248]Train operation and managementThe procedures and related equipment enabling a coherent operation of the different structural subsystem, both during normal and degraded operation, including in particular train driving, traffic planning and management^[249]Trainmaster, terminal manager, or road managerAn employee who supervises operations over a given territory^[250]Train orderThe process whereby signallers or dispatchers can change the order or timing of trains to maximise overall train service performance in real timeTrain setA toy train with its tracks, buildings, etc.^[251]TrainsetA group ofrolling stockthat is permanently or semi-permanently coupled together to form a unified set of equipment. Trainsets are most often used inpassenger trainconfigurations.TramA city-based rail system that typically shares its operational space with other vehicles and often runs on, across, or down the center of city streetsTram-trainTramsthat are designed to run both on the tracks of a city-based rail system and on the existingrailwaynetworks. Tram-trains' dual-voltage capability makes it possible to operate at lower speeds on city streets and at over 60 miles per hour (97 km/h) on main line tracks allowing travel in an extended geographical area without changing the method of transport.TreadleA mechanical or electrical device for detecting the presence of a rail vehicle with pin-point accuracy, unlike atrack circuit, which provides detection over an arbitrary distancesTurnout orpointsAswitchTurntableA section of track that rotates to let locomotives and rolling stock turn around or access several engine maintenance sidings in a small area

U

Unit trainA train in which allcars(wagons) carry the same commodity and are shipped from the same origin to the same destination, without being split up or stored en route^[252]

V

Vacuum brakeA continuous train brake that is fail-safe in operation. It is powered by avacuumfrom the locomotive but the application is actually byatmospheric pressurewhen the vacuum is released. Now largely superseded by theair brake.Valve gearThe linkage mechanism that operates the valve for a driving cylinder, to alternately admit steam to the cylinder and then exhaust it when the piston's stroke is nearly complete^[253]

W

StandpipeA device used for delivering a large volume of water into the tank or tender of a steam locomotiveWater gaugeor water glassA device showing the level of water in the boiler^[254]Way carAn alternate term for a caboose used by theChicago, Burlington and Quincy Railroad,Chicago and North Western Railway, andAtchison, Topeka and Santa Fe Railway^[254]Wayobjects or wayside objectsTrackside objects or any structures at the wayside or beside therail tracksusually within theright-of-way, such asrailway signals,third rails,overhead linesand their supports,electrification systems,platforms, orboom barriersWell tankA type oftank locomotive. The water tank is mounted between the frame plates, beneath the cab and boiler.Well wagon(UIC)Aflat wagonwith a depressed centre used for carrying extra tall loadsWheelThe rolling component typically pressed onto an axle and mounted on a rail car or locomotive truck or bogie. Wheels are cast or forged (wrought) and are heat treated to have a specific hardness. New wheels are trued to a specific profile before being pressed onto an axle. All wheel profiles must be periodically monitored to insure proper wheel to rail interface. Improperly trued wheels increase rolling resistance, reduce energy efficiency and may create unsafe operation. A railroad wheel typically consists of two main parts: the wheel itself, and the tire around the outside. A railway tire is itself steel, and is typically heated and pressed onto the wheel, where it remains firmly as it shrinks and cools.Wheel climbThe process of a wheel climbing up and often off the inside or gauge side of the rail. It is a major source of derailments. Wheel climb is more likely to occur in curves with wheels whose flanges are worn or have improper angles. See also:Adhesion railwayWheel flangeThe inner section of a wheel that rides between the two rails. The angle between the wheel tread and flange is often specific to the rail to prevent wheel climb and possible derailments. The wheel flange is part of the wheel tire. See also:Adhesion railwayWheel–rail interfaceThe on-contact interaction between wheels and rails. The term is used in connection with the design and management of their interaction.Wheel slipThe loss of traction due to aslippery railor wheel. Wheel slip was common with steam engines as they started to move due to the excessive torque often generated at low speed. Steam engines carried sand dispensing gear to increase traction at the start of motion.^[254]WheeltapperAn historical railway occupation; people employed to tap train wheels with hammers and listen to the sound made to determine the integrity of the wheel; cracked wheels, like cracked bells, do not sound the same as their intact counterparts. The job was associated with the steam age, but they still operate in some eastern European countries. Modern planned maintenance procedures have mostly obviated the need for the wheel-tapper.Wheel treadThe slightly conical section (often with a 1 in 20 slope) of a railroad wheel that is the primary contact point with the rail. See also:Adhesion railwayWhistleTrain whistles are used as a safety warning and also by the engineer to communicate to other railroad workers. Seetrain whistlefor a description of the whistle code used to communicate. Also a nickname for anair hornon a diesel locomotive. Steam engine whistles were historically known as chimes in the US during the 19th century.Whistle postAn advance warning to the engineer of an upcoming grade crossing. It is the point at which the engineer should begin sounding thewhistleorhorn.Whyte notationA system of describing steam locomotive wheel arrangements (e.g. 4-6-4, 2-10-2). The first number indicates the number of "pilot" wheels that help lead the engine into turns. The second is the number of coupled wheels ("drivers"). Third are the trailing idler wheels, usually to provide support to larger fireboxes. Articulated locomotives are similarly described. For example, a Union Pacific "Big Boy" would be described as a 4-8-8-4, wherein the pilot has four wheels, followed by two sets of drivers, eight wheels per set, and a four-wheel trailing bogie under the firebox. The numbers include the wheels on both sides of the engine, so a 2-8-2 engine would have one idler, four drivers, and a final idler on each side of the engine.WigwagA largely superseded Level or grade crossing warning signal that consists of a swinging disc facing road traffic, with a red light in the centre. The disc normally hangs straight down, but an approaching train sets it swinging from side to side, the red light illuminates or flashes, and a bell rings.Working water, foaming, or primingThe condition of a steam locomotive drawing water through its throttle valve, cylinders, and smokestack, often causing damage to the cylinders or running gearWrong-side failureA failure in a signalling system that leaves the system in a dangerous condition

Y

YardAn arrangement of tracks where rolling stock is switched to and from trains, freight is loaded or unloaded, and consists made up^[255][256]YellowA colour associated with a warning or a need to slow down when used by flags or signals, but the exact meaning varies from railway to railway

Z

Zig zagor switchbackA method of climbing and descending steep gradients, where shallow-gradient track reverses direction for a while, and then reverses again to continue in the original direction

See also

• Glossary of Australian railway terms

• Glossary of New Zealand railway terms

• Glossary of North American railway terms

• Glossary of United Kingdom railway terms

• Passenger rail terminology