Railroading Glossary
The following glossary is arranged alphabetically with each term catalogued by first letter. Select a letter below to begin.
A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q | R | S | T | U | V | W | X | Y | Z
A&S
Alton & Southern Railroad.
A1A-A1A
Diesel or electric locomotive wheel arrangement of two 3-axle trucks (wheel assemblies) in which only the outer axles of each truck are powered. The inner axle is an "idler" axle.
AAR
Association of American Railroads. The coordinating and research agency of the American railroad industry. It is not a government agency but rather an organization to which railroads belong, much as local businesses belong to a chamber of commerce.
Abandon
To cease operating all or part of a route or service, especially with the intent of never resuming it again
ABS
Automatic Block Signal System. Signal system that uses automatic block signals, cab signals, or both.
Adhesion factor
The percent of the total weight on a locomotive's driving wheels that is available for traction; also called adhesion coefficient, it's the measure of how well a locomotive grips the rail.
ADM
Archer-Daniels-Midland, a major agricultural company with more than 13,000 freight cars
AEI
Automatic Equipment Identification. System used by North American railroads to track cars and locomotives using data tags mounted on the sides of rolling stock. Trackside readers use radio signals to record the data-tag information as a train passes by.
Affiliate
A company effectively controlled or associated with others under common ownership or control.
Air test
Application of a train's air brakes at the start of a run to ensure they are functioning properly.
Alco
American Locomotive Company; also, a locomotive built by the American Locomotive Company.
Alco 251
The designation for the engine used in Alco's locomotives from 1953 to 1969 and since then by Montreal Locomotive Works and Bombardier. The "2" indicates a 9-inch cylinder diameter and 10-inch stroke; "51" is for the year it was first tested. Predecessor Alco engines were the 244 for road locomotives and the 539, primarily for switchers.
All black
No defects visible on the side of the train, especially hot boxes or sticking brake shoes, which would stand out from the otherwise black running gear.
All-weather cab
A steam locomotive cab enclosed at the rear to provide the crew with protection from harsh weather. Also called vestibule cabs.
American Short Line Railroad Association (ASLRA)
A trade association of railroads and suppliers that provides legislative, management, and traffic assistance to short lines.
Angle bar
Short pieces of steel used to join together standard sections of rail (usually 39 feet). Four bolts, fastened through a pair of holes at each end of the angle bar, are used to join the rails together.
Angle cock
Valve located at the ends of locomotives and cars. In the open position, allows brake-pipe air to flow from car to car; when closed (as on the end of a train), keeps air in system.
Anti-climber
Extensions to the frame at each end of a diesel locomotive, which prevent objects that a moving train might strike from "climbing" up onto the engine and causing injury to the crew and damage to the equipment.
APCU
See Auxiliary power-cab unit.
Approach-lit signal
Signals that light up only when the presence of a train automatically completes electrical circuits between the two rails. Saves electric power and light-bulb life.
APU
Auxiliary power unit.
ARA
American Railway (or Railroad) Association, a predecessor of the Association of American Railroads.
Armstrong turntable
Any old-style equipment that relies solely on muscle power, in this case a turntable that must be rotated by hand. A steam engine that lacks an automatic stoker is sometimes called an "armstrong".
Articulated
A steam locomotive with two sets of driving wheels under a single boiler. Articulated locomotives have wheels arrangements such as 2-8-8-4 or 4-6-6-4. Articulated rolling stock, such as certain types of passenger cars and double-stack cars, share trucks between adjacent car bodies.
ASEA
Allmänna Svenska Elektriska Aktiebolaget (Universal Swedish Electric Co., Ltd.), Swedish locomotive manufacturer, which merged with the Swiss firm Brown Boveri to form ASEA Brown Boveri.
Association of American Railroads (AAR)
The coordinating and research agency of the American railroad industry. It is not a government agency but rather an organization to which railroads belong, much as local businesses belong to a chamber of commerce.
ATC
Automatic Train Control. A system of cab signals and other safety features for which specially equipped locomotives are required. If a train exceeds the permissible speed for a given signal indication, the brakes are automatically applied.
ATS
Automatic Train Stop. System of lineside and locomotive-mounted equipment, which produces an application of a train's brakes should its engineer not acknowledge a restrictive signal within 20 seconds of passing it. Required for speeds over 79 mph.
Auto rack
A flatcar equipped with decks, walls, roof and end doors for transporting automobiles and light trucks on two or three levels. (Also referred to as a "multi-level" car.)
Automatic Block Signal System (ABS)
Signal system that uses automatic block signals, cab signals, or both.
Automatic block signals
Provides automatic control of signals using electric track circuits. By dividing a track into separate sections (called "blocks") which are insulated from each other electrically, and making the blocks part of electric circuits which include lineside signals, a system of automatic train protection is achieved. When a train is in a block, it completes the circuit that automatically sets the signal behind it (and ahead of it, if the line is signaled for movement in both directions) to red.
Automatic Train Control (ATC)
A system of cab signals and other safety features for which specially equipped locomotives are required. If a train exceeds the permissible speed for a given signal indication, the brakes are automatically applied.
Automatic Train Stop (ATS)
System of lineside and locomotive-mounted equipment, which produces an application of a train's brakes should its engineer not acknowledge a restrictive signal within 20 seconds of passing it. Required for speeds over 79 mph.
Auxiliary power-cab unit (APCU)
Push-pull operation of passenger trains requires an engineer's cab on the opposite end of the train from the locomotive. The APCU is a diesel cab or A unit which provides that cab and also has been rewired to supply power for heat, light, and air conditioning to passenger trains instead of tractive power.
Availability
The time a locomotive is free from disabling mechanical defects between scheduled maintenance dates, and thus available for revenue service. Availability is usually expressed as a percentage over a specified period of time, usually a month.
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