Rail terminology

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Two rail welds in continuous welded rail in Wisconsin.

Rail terminology is a form of technical terminology. The difference between the American term railroad and the British term railway (also used by other English-speaking countries outside the U.S.) is the most obvious trans-Atlantic difference in rail terminology (see usage of the terms railroad and railway for more information). There are also several others, caused by the parallel development of rail transport systems on both sides of the Atlantic. Various terms are here presented alphabetically; where a term has multiple names, this is indicated. The note "U.S." indicates a term peculiar to the North American continent, while "UK" refers to terms originating in the British Isles and normally also used in former British colonies outside North America (such as Australia, New Zealand, etc.). Exceptions are duly noted; terms whose currency is limited to one particular country, region, or railway are also included.

For terminology specific to the types of lines used for passenger trains, see passenger rail terminology.

:	Top - 0–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

0-9

Note: for 4-4-0, 2-6-4T, 0-4-4-0, etc. see Whyte notation or UIC classification

• 10 wheeler (U.S.): locomotive with a 4-6-0 wheel arrangement

A

• Air brake: railroad brakes which operate using air compression
• Alco: American Locomotive Company - the second largest builder of steam locomotives in the U.S.

An American class steam locomotive

• American: locomotive with a 4-4-0 wheel arrangement
• Annett’s key (UK): a token in the form of a key which fits point levers in the section which it controls. It cannot be removed to hand back to the signaller unless the points are locked in position for the through line.
• Articulated locomotive: a steam locomotive with one or more engine units that can move relative to the main frame
• Atlantic: locomotive with a 4-4-2 wheel arrangement
• A unit (U.S.): a locomotive with a driving cab, or crew compartment, for operating on the road. When equipped with MU, it can control other A units, or B units.
• Auto-brake gauge: A gauge recording the application and pressure of an automatic braking system; usually repeated in the guard's van in historic rolling stock.
• Automatic train operation (ATO)
• Automatic train protection (ATP)
• Automatic Warning System (UK): refers to the specific form of limited cab signalling introduced in 1948 in the United Kingdom to help train drivers observe and obey warning signals.
• Autorack (also called auto carrier) (U.S.): a specialized freight car for transporting automobiles. Car transporter wagon / Car transporter van (UK).
• Auto train (UK): a branch line train consisting of a steam locomotive and passenger carriages that can be driven from either end by means of rodding to the regulator and an additional vacuum brake valve. The fireman remains with the locomotive and, when the driver is at the other end, the fireman controls the cut off and vacuum ejectors in addition to his usual duties. Also: Push-pull train, Motor train.
• Auto Train (U.S.): A passenger train service first operated by Auto Train Corporation and then by Amtrak between Lorton, Virginia and Sanford, Florida that carries the passengers' automobiles aboard the same train in autoracks.

B

• Bacon slicer (UK): Slang term for a cutoff controlled by a wheel operating through a worm and nut, rather than the more usual quadrant lever. The device was slow to operate, but very precise, and therefore only fitted to long-distance locomotives where frequent changes of cut-off were not required.
• Baldwin: American locomotive manufacturer.
• Ballast : aggregate stone, gravel or cinders forming the track-bed on which sleepers (ties) and track are laid to ensure stability and proper drainage.
• Bank : a particularly steep section of line that requires additional bank (or banking) engines (U.S.: booster engines) to help trains climb.
• Baobab: (PRR only): an oversize load. From the telegraph code-word used. A baobab tree is a very large tropical tree.
• Base plate (UK), saddle (rail) (U.S.): an iron or steel plate used to spread the weight of rail over a larger area of sleeper and facilitate a secure, low maintenance, fastening with bolts or clips.
• Bay platform: a type of platform/track arrangement where the train pulls into a siding, or dead-end, when serving the platform.
• Beep: a one-of-a-kind switcher locomotive (also referred to as the SWBLW) built by the Atchison, Topeka and Santa Fe Railway in 1970.
• Blower: A steam pipe leading into the smokebox, causing necessary draft in the stack when the engine is not running. However, UK practice is to turn on the blower also when entering tunnels, etc, to avoid dangerous blow-back into the cab. The UK loading gauge is much smaller than that in the U.S. and the tunnel roof would otherwise spoil the normal draft created from the exhaust.
• Bobber: (archaic, U.S.): a slang word for a small caboose with just four wheels, all rigidly mounted to the frame. This design was common in the 1800s. Bobber refers to the bouncing or bobbing motion made by such a caboose when in motion.
• Bo-Bo (Europe): a locomotive with a 4 wheel per truck configuration, each individually powered, as opposed to a 6-wheel "Co-Co" configuration.

Bettendorf-type freight car bogie/truck; note the solid bearings around the ends of the axles.

• Bogie (UK), truck (U.S.): The undercarriage assembly incorporating the wheels, suspension, brakes and, in powered units, the traction motors.
• Boiler: a cylindrical container adjacent to the firebox in which steam is produced to drive a steam locomotive.
• Bonds: Short wires used to bridge gaps in electrical circuits, usually at track circuit joints or between rails.
• Booster: (steam locomotive) - an extra set of cylinders that can be engaged to drive a trailing truck or tender truck to give additional tractive effort at starting and low speeds; (U.S.) (diesel locomotive) - a cabless B unit
• Boxcar (U.S.): a type of rolling stock with a flat-bottomed rail car enclosed on all sides and above, which is loaded and unloaded from sliding doors on each side. Same as van (UK).
• Brakeman: a train crewmember who performs railcar and track management; often a single job description along with switchman ("brakeman/switchman"). Originally a brakeman performed manual activation of brakes on railroad cars before the advent of the air brake.
• Brake van (UK): A heavy vehicle with powerful brakes which was attached to the rear of goods trains in the days when most wagons were not fitted with a continuous braking system. Its function was to supplement the locomotive's braking power in slowing and stopping the train and, very importantly, to keep the couplings uniformly tight by selective light braking to avoid snatching and breakages. It also conveyed the train guard, hence its alternative name of "guard's van". Partly analogous to caboose (U.S.) and its synonyms.
• Branch line: a secondary railway line that branches off a main line.
• Broad gauge: track where the rails are spaced more widely apart than 1435 mm (4 ft 8½ in) (which is called standard gauge). Many early railroads were broad gauge, for example the Great Western Railway in the UK which adopted 7 ft 1/4 in (2141 mm) gauge until it was converted to standard gauge in the 1860s - 1890s. Russia still has over 80,000 km of broad gauge (1520 mm or 5 ft) railroads. Broad gauge is also normal in Spain, Portugal, and India (1680 mm or 5ft 6ins), as well as Ireland (1600 mm or 5ft 3ins). It is also still used in Australia (1600 mm).
• Bubble Car: A DMU consisting of a single coach (UK).
• Buckeye coupler: A particular form of coupler which will lock automatically when the two parts are pushed together.
• Buffer a device that cushions the impact of rail vehicles against each other.
• Buffer stop (UK): the barrier installed at the end of a dead-end track to prevent rail vehicles from proceeding further. Bumper (U.S.).
• Buggy (slang, U.S.): a caboose on the Boston and Maine Railroad.
• Bull head rail (UK): A steel rail section commonly used in 60ft lengths on almost all railway lines throughout Britain until c1950, which on account of its shape needs to be supported in cast iron chairs that are screwed to the sleepers. It is still found on secondary and preserved lines and in the yards.

ATSF 331, a GP60B B unit.

• B unit (U.S.): a cabless booster locomotive, controlled via MU from a cab-equipped A unit.

C

A string of cabooses in Ohio.

• Cabin car (PRR): see caboose.
• Caboose (U.S.), cabin car (PRR), way car (CBQ), crummy (slang, U.S.), hack (slang, U.S.): a railroad car attached usually to the end of a freight train, in which railroad workers could ride and monitor track and rolling stock conditions. Partly analogous to brake van (UK). Largely obsolete, the vehicle in question having been replaced by the electronic End of Train (EOT) device, or Flashing Rear End Device (FRED).
• Cant: angle. Can be used in the context of the cant of the rail track (the relative level one rail with another); and the cant of a rail, being the angle of that single rail relative to the perpendicular.
• Carbody unit or cab unit (U.S.): a locomotive which derives its structural strength from a bridge-truss design framework in the sides and roof, which cover the full-width of the locomotive. It refers to both A units and B units.
• Catenary or catenary structure : the overhead wire system used to send electricity to an electric locomotive or multiple unit.
• Centralized traffic control (CTC): a system in which signals and switches for a given area of track are controlled from a centralized location. May or may not be computerized.
• Cess (UK): the area either side of the railway immediately off the ballast shoulder. This usually provides a safe area for authorised workers to stand when trains approach
• Chair (UK): A cast iron bracket screwed to the sleeper and used to support bull head rail that is held in place by a wooden key (wedge) or spring steel clip. Still to be found on preserved railways and in yards.
• Ches-C (U.S.): Chessie System's kitten logo.
• Chimney (UK): smokestack or stack (U.S.), or funnel.
• '''Chopper: Enthusiasts nickname for BR Class 20 locos.
• Co-Co (Europe): a heavier duty locomotive with 6 wheels per bogie configuration as opposed to a 4-wheel "Bo-Bo" configuration. The correct classification is Co'Co', but Co-Co is used more often.
• COFC: abbreviation for "Container On Flat Car".
• Colour-light signals (UK): Signals the aspects of which are conveyed by lights alone; they may have 2, 3, 4 or more aspects.

A compound locomotive on British Railways in 1948.

• Compound locomotive: a steam locomotive passing the output steam through two sets of cylinders. One set uses high-pressure steam and passes the "low-pressure" steam on to the second.
• Compromise joint: A special joint bar used to join rail ends of two different cross-sections while holding the top running surface and inside gauge surface even.
• Conductor (U.S.), guard (UK): the person "in charge" of a train and its crew. On passenger trains, a conductor is also responsible for tasks such as assisting passengers and collecting tickets.
• Consist (U.S.), formation (UK): a noun to describe the group of rail vehicles which make up a train.

• Continuous welded rail (CWR)
• Control Point (CP) (U.S.): an interlocking, or the location of a track signal or other marker with which dispatchers can specify in the control of trains.
• Coupler (U.S.), coupling(UK): Railroad cars in a train are connected by couplers located at the ends of the cars.
• Coupling rods: Rods between crank pins on the wheels, transferring power from a driving axle to a driven axle
• Cowl unit (U.S.): a locomotive whose sides and roof are non-structural, and cover the full width of the locomotive. Structural strength comes from the underframe.
• Crank pin a pin protruding from a wheel into a main or coupling rod
• Crosshead the pivot between the piston rod and the main rod on a steam locomotive.
• Crummy (slang, U.S.): a word used for a caboose in deplorable condition.
• Cut off: A variable device on steam locomotives which closes the steam valve to the steam cylinder before the end of the piston stroke, thus conserving steam from the boiler while allowing the steam in the cylinder to expand under its own energy. Also: Reverser.
• Cylinder

D

• Dead man's handle: A safety mechanism on a train controller which automatically applies the brake if a lever is released. It is intended to stop a train if the driver is incapacitated.
• Detonators: Small charges placed on the running rail which explode when run over; used to warn drivers in following trains of an incident ahead. Also called torpedoes (U.S.).

Railroad crossing at grade, also known as a diamond. This example is located in Mulberry, Florida.

• Diamond: Trackage which allows a rail line to cross another at grade.

A DMU in Poland.

• Diesel multiple unit or 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 termed railcars.
• DOO: Driver-only operation
• Doodlebug: Gasoline-electric self-powered passenger car used for small capacity rural commuter service.
• Down (UK): a direction (usually away from London, other capital city, or the headquarters of the railway concerned) or side (on left-running railways, the left side when facing in the down direction). The opposite of up. The down direction is usually associated with odd-numbered trains and signals.
• Driver (UK), Engineer (U.S.)
• Driver (UK): Steam locomotive driving wheel, particularly in "single driver" (one driven axle) engines.
• Driving van trailer or DVT: an end carriage from which the train can be driven when the locomotive is at the rear of the train, push-pull operation.

E

• Ejector: Component of vacuum brake system. Steam passing through a cone sucks air from the train pipe to create the vacuum. Usually fitted in pairs: 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 ("making a brake" – UK) after coupling up.
• Electric multiple unit or EMU: a set of electrically powered self-propelling passenger rail vehicles able to operate in multiple with other such sets.

Three BN locomotives coupled "elephant style".

• Elephant style (U.S.) - railfan jargon to describe how multiple locomotives are coupled together in a train; the front of the second locomotive is coupled to the rear of the first locomotive, the front of the third locomotive is coupled to the rear of the second locomotive, and so on down the line. The term is reminiscent of a parade of circus elephants where the elephant behind the front elephant would hold the leading elephant's tail in its trunk.
• Elevated railway: one typically built on supports over city streets, also just "the el"
• EMD: Electro-Motive Diesels, Inc, the world's largest builder of railroad locomotives.
• Engineer (U.S.): driver, engine driver, train driver (UK)
• EOT (U.S.): End of train device; same as FRED (see below).
• EP gauge (UK): Electro-pneumatic brake gauge; recording the application and pressure of the service brake, usually repeated in the guard's van in historical rolling stock.
• Event recorder - a 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 Adminitration (FRA) for freight, passenger and commuter rail. Regulations for railroad outside the U.S. vary by country. Transit operations are not generally mandated to have event recorders but have begun to add them anyway.
• Ex-con (U.S.): An ex-Conrail locomotive (jargon).
• Express train: a train that runs through selected stations without stopping.
• Extra train: A train that is not included in normal scheduled operations of a railroad. Normally, extras are required to clear the main line for scheduled trains to pass.

F

• Facing: a turnout is facing if it can select which way to diverge a train. Opposite of trailing.
• Fairlie: type of articulated locomotive, typically (but not exclusively) with two boilers and connected fireboxes in a central cab.
• Fallen flag (U.S.): a railroad which is no longer in business, having either merged or discontinued operations.
• Feedwater heater: a device to preheat the water for a steam locomotive; improves efficiency.
• Fettle, fettling: making repairs to rail track, especially concerned with maintaining the drainage of the ballast, and the proper cant of the rail track and rails.
• Fiddle Yard: used in model railways to provide more realistic operation in limited space.
• Firebox: in steam railroading, a firebox was a chamber in which a fire would produce sufficient heat to create steam once the hot gases from the firebox were carried into the adjacent boiler via tubes or flues.
• Fireman: a worker whose primary job is to shovel coal into the firebox and ensure that the boiler maintains sufficient steam pressure; a driver's assistant.
• Fishplate (UK), Joint bar (U.S.): joins the ends of rails in jointed track. Also the steel plate between rails and ties

• Flatcar (U.S.): a type of rolling stock, which can be a flat-bottomed car with no sides on which freight (including intramodal shipping containers) can be stacked. A bulkhead is a flatcar with walls on the front and back. A center-beam bulkhead is a bulkhead flatcar with an additional wall dividing one side of the flatcar from the other, but still without any sides. Flat wagon (UK).
• Flying junction: a 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 over in front of opposing traffic.
• Foamer (U.S.): colloquial term for a railfan, specifically one whose enthusiasm is unreasonably excessive, "foaming at the mouth".
• Four-foot: the part of the line between a pair of running rails. An abbreviation for four foot, eight-and-a-half-inches. See also six-foot and ten-foot.
• FRA: (U.S.) the Federal Railroad Administration. This agency overseas all rail operational regulations and safety requirements for U.S. freight, passenger and communter rail operations.
• FRED: (U.S.) Flashing rear-end device
• Free-mo: type of modular layout in model railroading
• Freight (U.S.): goods (UK)
• Frog: (U.S.) casting with "X" shaped grooves used in switches and crossovers.
• Funnel: a Thomas the Tank Engine misnomer for a chimney (UK) or smokestack (U.S.), although it is also used in Australia (Victoria at least).

A brakeman on the Indiana Harbor Belt Railroad uses a fusee to demonstrate a hand signal indicating "stop".

• Fusee: A pyrotechnic device similar to an automotive flare that is used for signalling.

G

• Gage: an alternate (U.S.) spelling of "Gauge" as in "track or rail gage".
• Gandy dancer (slang, U.S.): A track maintenance worker.
• Garratt: type of articulated locomotive
• Gauge: the width between the rails.
• Geep: A slang term for any of the GP ("general-purpose") series of Electro-Motive four-axle diesel locomotives; originally applied only to EMD GP7, GP9, and GP18 models.
• Gondola: a type of rolling stock with a flat bottom and relatively low sides, used to haul material such as ore or scrap, and loaded and unloaded from the top. May be covered or uncovered. Open wagon (UK).
• Goods (UK): freight (U.S.): both terms are used in Australian English
• Grab bar: handle on the side of a car to allow switching personnel to hold on safely
• Green: a colour associated with go or proceed.
• Guard (UK): conductor (U.S.) In Australia, the latter is used for tram conductors, guard is more common on trains.
• Guard Rail (U.S.) Check rail (UK): A double rail section of track, sometimes found in train yards and on bridges to prevent derailments, by having rail on both sides of the wheel flange. Also found on curves with a tight radius and switches and crossings
• Gunzel (AUS) Railway enthusianst, in Melbourne, Victoria often refers to tramway enthusiast.

H

• Hack (slang, U.S.): a caboose, since it carried the crew around like a taxicab.
• Hammerhead style (slang, U.S.): the practice of running a Diesel locomotive with its long hood forward. This has been done for a variety of reasons, such as crew safety in case of a collision. On short runs, operating the locomotive "backwards" is more economical than using a wye or turntable or operating a second locomotive. Some locomotives may have a second control stand to facilitate operation in the "reverse" direction.
• Handcar, a small, hand-powered railroad car used for track inspection.
• Head end power or HEP: a scheme whereby the locomotive engine (rather than a separate generator) provides power to carriages.
• Heavy rail (U.S.): a city-based transit rail system that runs on its own dedicated track and often underground. Subways are considered heavy rail.
• High rail : the upper rail in a curve or superelevation which typically experiences the higher lateral loads and greater wear.
• Hogger (slang, U.S.): a locomotive engineer.

TPW 400, an ALCO RS-11, a type of hood unit.

• Hoodlebug (slang, U.S.): a small commuter passenger train or trolley.
• Hood unit (U.S.): a locomotive whose sides and roof are non-structural and do not extend the full width of the locomotive. Structural strength comes from the underframe.
• Hoover: Enthusiasts nickname for BR Class 50 locos.
• Hotbox: An axle end that has gotten too hot due to friction in the journal bearing.
• Hotbox detector: A device attached to the track which monitors passing trains for hot axles, and typically then reports the results via a radio transmission (U.S.) or a circuit to the signal box (UK). (see defect detector).
• Hotel power (U.S.): that power used to provide for the comfort of passengers aboard a train en-route. See "HEP" above.
• Hotshot (U.S.): a fast, long-distance train given priority on the track over other trains.
• Hump: a raised section in a rail storage yard that allows operators to use gravity to move freight railcars into the proper storage position within the yard (i.e., humping the cars).
• Hunting: swaying motion of a railway vehicle caused by the coning action on which the directional stability of an adhesion railway depends.

I

• Injector: device to force water into a steam locomotive's boiler by steam pressure.
• Interlocking (U.S.): any location that includes a switch or crossing of two tracks, derived from the early practice of installation of a system of mechanical equipment called an interlocking plant to prevent collisions. See also Interlocking tower and signal box. Interlocking is also the term for the actual mechanical or electrical apparatus that prevents switch/points and signals from being operated in ways that would allow for conflicting train movements.
• Intermodal: moving goods or people by more than one type of vehicle. Intermodal freight can be transported using shipping containers which can easily be transferred among railroad flatcars, ships, airplanes, and tractor-trailer trucks.
• IRJ, IBJ: Insulated rail joint/insulated block joint. Rail joints incorporating insulation to isolate individual track circuits.

The interlocking tower and tracks at Des Plaines, Illinois, in 1993.

• Island platform: a railway platform that has tracks along the full lengths of both sides.

J

• Johnson bar (US): On a locomotive, a long, heavy lever that operates the cutoff.
• Joint bar, fishplate (UK): joins the ends of rails in jointed track.
• Jointed track: track in which the rails are laid in lengths of around 20 m and bolted to each other end-to-end by means of fishplates (UK) / joint bars (U.S.).
• Junction: A point at which two lines or separate routes diverge from each other.

K

• Key (UK): Timber or sprung steel block used to secure Bull Head rail into the chairs.

L

Lantern (U.S.): A portable (often handheld) light source that is used to signal train crews. Lamp (UK).

M

• Mainline or Main line: A track that is used for through trains or is the principal artery of the system from which branches, yards, and spurs are connected; a route between towns, as opposed to a route providing suburban or metro services. Mainline tracks are typically at higher speeds than branch lines and are usually maintained and built to a higher standard than yards and branch lines.
• Main rod (U.S.): The drive rod connecting the crosshead to a driving-wheel or axle in a steam locomotive. Connecting rod (UK).
• Maintenance of way (U.S.): The maintenance of railroad rights of way, including track.
• Mallet (pronounced "mallay"): type of articulated locomotive designed by Anatole Mallet. See "Compound Engine" above.
• Matchbbox tank (UK slang): a type of pannier tank where the tanks are square and do not rest of the locomotive frame - see illustration.
• Mating worms (U.S.): Penn Central logo (jargon/slang).
• Mechanical semaphore signal: A signal the aspect of which is conveyed by moving an arm in addition to a light.
• MLW: Montreal Locomotive Works, bought by Bombardier and closed.
• Mogul: locomotive with a 2-6-0 wheel arrangement
• Motor train (UK): See Auto train (UK) above.
• Multiple aspect signalling: A system of colour-light signalling in which signals may show 3 or 4 aspects.
• Multiple unit (UK): 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) and Electric Multiple Unit (EMU) are more common terms. These may also be termed railcars.
• Multiple unit (U.S.), Multiple working (UK): generally seen as the abbreviation MU, this normally refers to the ability of diesel and electric locomotives or multiple units to be joined together and controlled from one driving station. Such a set of joined locomotives is called (U.S.) a consist or (colloquially) "lash-up" and is said to be "MUed together".
• Multiple working (UK): see Multiple unit (above).

N

Comparison between standard gauge (blue) and one common narrow gauge (red) rail spacing.

• Narrow gauge: railroad track where the rails are spaced less than 1435 mm (4 ft 8½ in) apart. There are many common gauges narrower than standard, amongst them 3 ft 6 in (1097 mm) widely in Africa and Asia; 3 ft (914 mm), which was the most common narrow gauge in the U.S.; and 2 ft (600 mm), which saw widespread use in the UK. Meter gauge (1000 mm) is also been used. Narrow-gauge lines are often found in mountainous terrain where the cost savings of building a smaller railroad can be considerable.

O

• Open wagon (UK), Gondola (U.S.).
• Overlap (UK): A distance (normally 200 yards) beyond each signal which must be clear before the preceding signal can display a proceed aspect; allows a margin in case a train overshoots a signal before stopping.

P

• Pacific: locomotive with a 4-6-2 wheel arrangement

A Pannier tank steam locomotive.

• Pannier tank: a tank locomotive with the water tanks mounted on the boiler like panniers.
• Pantograph: arm to pick up current from overhead lines
• Per diem: fee paid by a railroad to the owner of a car for the time it spends on the railroad's property. Pronounced by U.S. railroaders per die-um, not per dee-um.
• Piston: the moving part in a steam engine cylinder that translates the steam pressure into motion
• Point machine (UK): A motor or device which operates points.
• Points (UK): switch (U.S.). Also "turnout".
• Pony truck: a two-wheel truck (U.S.) or bogie (UK) at the front of a locomotive
• Pound (rail): term for weight of the rail
• Prairie: locomotive with a 2-6-2 wheel arrangement
• Push-pull: a mode of operation whereby a locomotive-hauled train may be driven with the locomotive at the front, middle or back of the train. Also: Auto train (UK), above. See Top and tail for train with locomotives at both front and back.

Q

R

• Railbus: a DMU the size of a bus, sometimes made using bus components.
• Railcar: another term for Diesel Multiple Unit - DMU
• Railfan: a hobbyist or enthusiast of trains
• Rail profile the specific shape of the rail. There are many different rail profiles which are often specific to individual railroads. Rails need to be periodically scanned electronically, the data inspected and analyszed, 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 entirely.
• Railroad car: a railroad vehicle that is not a locomotive.
• Railroadiana: artifacts of currently or formerly operating railways around the world.
• Railway station (UK, sometimes U.S.); train station (U.S., now supplanting railway station in UK also.)
• Red: a colour generally associated with stop, when shown by signals or flags.
• Rent-a-Wreck (slang, U.S.): A (usually old) locomotive owned by a leasing company.
• Reporting mark: a two- to four-letter code, assigned by the Association of American Railroads, that is applied to equipment operating on North American railroads to uniquely identify the owner of the equipment.
• Reverser: see Cut off, above.
• Right-side failure: A failure in a signalling system which leaves the system in a safe condition
• Rolling stock: a railroad vehicle that is not a locomotive; synonymous with railroad car.

S

• Saddle: a plate which is bolted to sleepers, holding the rails in place.
• Saddle tank: a tank locomotive with the water tank mounted on top of the boiler like a saddle.
• Safety Appliance Act (U.S.): law mandating air brakes, grab bars, and automatic couplers
• Safeworking: the system of rules and equipment designed to ensure the safe operation of trains.

Semaphore type signals in Kościerzyna, Poland.

• Schnabel car: A specialized type of freight car for extra heavy and oversized loads; the car is loaded in such a way that the load forms part of the car superstructure.
• Searchlight: a signal with a single light source usually capable of displaying three different colors. Complex internal mechanisms govern which color is displayed.
• Section: the division of the track for security (occupation).
• Semaphore: a type of signal that has a mechanical moving arm; any signalling using semaphores.
• Shay: A type of geared steam locomotive built to the patents of Ephraim Shay.
• Shoofly: A temporary stretch of track that takes trains around construction or an accident scene.
• Shunt (UK): to move trains or vehicles from one track to another.
• Shunt (U.S.): to bond the rails/power feeds between sections on trolley/light rail systems, so as to temporarily bridge past dead areas.
• Shunter (UK): switcher (U.S.) or shifter (PRR only): a small locomotive used for assembling trains and moving railroad cars around. Also, a person involved in such work.
• Shuttle service: a train, usually a passenger service, that runs back and forth over a relatively short distance, such as between a junction station and a branch-line terminus.
• Side tank: a tank locomotive with water tanks mounted each side of the boiler.
• Siding: a section of track off the main line used for storing rolling stock or freight. In the U.S. the term is also used to cover the British term: loop.
• Signal: a device that indicates to the driver of a train information about the line ahead.
• Signal aspect: The colour shown on a signal, or the position of the arm on a semaphore signal, ncluding the track status. In the UK, multiple aspect signals are:
• *green = clear
• *red = stop
• *double yellow = preliminary caution (the next signal is likely to be at caution)
• *single yellow = caution (the next signal is likely to be red)
• Signal-box: A building or room at a station which houses signal levers (usually in a frame) or panel.
• Signal Passed At Danger or SPAD (UK): where a train disobeys a stop signal.
• Six-foot: the narrow corridor between a pair of closely-spaced tracks, measuring six feet, and the most dangerous place to stand. The boundary between the six-foot, where one may be hit by a train, and the wider designation/width of the ten-foot, where one is usually safe, is hard to judge. See also four-foot and ten-foot.
• Sleeper (UK), tie (U.S.): bars placed at 90° to the rail tracks to support the rails. Generally of wood, concrete or steel, with various contraptions to affix the rails to the sleeper. Usually spikes, nails or bolts are used. Note in the UK baseplates and clips are used to affix the rail to the sleeper
• Smokebox: enclosed (normally cylindrical) space attached to the end of the boiler opposite the fire on a steam locomotive (normally the front). Supports the stack/chimney; steam pipes to and from the cylinders pass through here; contains the blastpipe/exhaust nozzle where the exhaust steam is used to provide draft for the fire. In superheated locomotives, also contains the superheater header and (optionally) a front-end throttle. A smokebox door allows access for cleaning.
• Smokestack (abbr. stack) (U.S.): chimney (UK)
• SPAD (UK): Signal Passed At Danger, where a train disobeys a stop signal.

Two unused and one heavily corroded spikes. The measurement scale shown is inches.