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AAR Association of American Railroads. Represents the railroad industry in areas such as public relations, and advertising and establishes safety and equipment standards.
AB Valve The operating device used on freight cars for charging, applying, and releasing the brakes. Also known as a triple valve.
Abandon When a railroad ceases operation over a route with no intention of resuming service.
ABD Valve An improvement of the AB Valve that features a quick release.
ABDW Valve Improved version of the ABD Valve. Modifies the Emergency Portion of the brake system and provides for accelerated buildup of brake cylinder pressure during quick service applications.
ABS 1) See Automatic Block Signal. 2) [MR] A modeling plastic which is harder than Styrene.
Absolute Block A length of track in which no train or engine is permitted to enter while it is occupied by another train or engine.
Absolute Permissive Block (APB) A designated section of track or tracks within which the movement of trains will be governed by block signals, whose indications supersede the superiority of trains. The block signals may be controlled manually or automatically.
Absolute Signal A block or interlocking signal designated by an "A" marker or the absence of a number plate.
Abutment A foundation designed to hold back the pressure of solid ground, such as an end pier of a bridge.
ACC Alphacyanoacrylate, Super glue, also called "CA". A high-strength adhesive that can be used on metal and styrene plastic.
Accelerometer A device which measures a trains rate of speed change.
Accessorial Pricing Charges for any services performed that are incidental to line-haul transportation, such as weighing and switching cars.
Accommodation A local train which makes all stops.
ACI Automatic Car Identification. See "Kar Trak".
Active Dynamic Braking Using the traction motors as generators whose output is dissipated in a massive resistor bank. The effect being to consume the trains momentum in generating electricity.
Add To couple car(s) to a train.
Adhesion The amount of pulling or retarding force a wheel is capable of exerting on the rail without slipping or spinning. The base coefficient of friction between the wheel and the rail, are the determining factors and those factors are affected by the load on the wheel, wheel and rail condition and external factors such as oil, rust & weather.
Adhesion Coefficient The ratio of tangential and normal force that exist between the wheel and the rail during motion.
Adhesive Weight The total of the driving-wheel axle loads.
Advertised Time as per schedule on timetable.
AEI Automatic Equipment Identification (such as bar code readers).
Age Seniority, length of service.
Airbrake A braking system in which compressed air is used as the operating medium.
Airbrake System All of the operating devices, pipes, fittings, and foundation brake gear used for controlling the speed and stopping a locomotive or train.
Airbrush A miniature paint sprayer that gives a controlled application of thinned paint.
Air Flow Indicator An instrument that measures the air flow through the automatic brake valve to the brake pipe.
Air Monkey Air brake repairman.
Air Problems Any issues associated with the train line or air brake system, including leaking gasket, frozen or blocked train line, stuck triple valve.
Alertness Device A device that initiates a penalty brake application when the engineer does not maintain the required frequency of movement. - A "deadman" type of safety device.
Alignment Control Couplers Specially equipped couplers that limit lateral movement and reduce lateral forces on the track. These couplers minimize rail turnover, wheel climb, and jackknifing.
All Darkie, No Sparky (Hi-Ball on a roll by).
Alley A clear and open track, usually in a switching yard.
Alternating Current (AC) An electric current that reverses its direction of flow at regular intervals. Each move from zero to maximum strength and back to zero is known as a cycle.
American Railway Engineering Association A railroad industry professional engineering association based in Washington, DC.
Ammeter Meter used to measure current strength; How many amperes are being used by a motor or other electrical equipment.
Ampere or Amp Unit used to measure electrical current strength.
Amtrak Name (not an acronym) for the National Rail Passenger Corporation, a government-subsidized railroad. Amtrak's home page is
Anchor Them Set hand brakes on still cars, the opposite is release anchors.
Angle Bars Short pieces of steel used to join track sections to other sections or track structures. An angle bar is placed on each side of the sections being joined. Holes are drilled into each end of the angle bar and also through both track sections. Bolts with locking washers are fastened through the holes to join the sections. Angle bars also are used to make temporary repairs to a broken section of rail until it can be replaced. Also known as "fishplates".
Angle Cock A device used for the purpose of opening or closing brake pipe on ends of cars, rear ends of tenders, and front ends of switch engines so equipped. Provision is made for supporting hose at proper angle.
Anti-climber Horizontal ribbing on the ends of engines and older cars which prevented car floors from jumping up and penetrating adjacent cars during a collision. Anti-climber brackets are also used on mining locos.
APE All Purpose Employee. An employee that is a promoted engineer that can also be forced to work as a conductor or trainman.
Application Consists of all of the operations from the time the brake pipe reduction is started until the brake is released.
Approach Signal A signal that governs the approach to another signal.
Approach Warning System A railroad signaling system that provides a signal as a train approaches an area of track, such as a roadway crossing.
Apron Overlapping deck between the cab and a tender; Hinged covering above locomotive and tender connection.
Arbor Wheel axle.
Arc Spark created by passage of current across a gap; also a curve.
Arch A shallow, semicircular configuration, usually constructed of firebrick or similar material, in a steam locomotive firebox below the tubes. It is intended to promote more efficient fuel consumption and reduce the amount of smoke while protecting the flue tubes.
Armature The wire-wound rotating part of a motor.
Armstrong Old-style equipment operated by muscular effort, such as hand-brakes, some turntables, engines without automatic stokers, etc.
Arrival Track The track which passenger trains arrive at a terminal; or freight trains arrive in or near a yard.
Articulated Car A car constructed by permanently connecting two or more platforms with an articulated joint (two platforms share a common truck).
Articulated Locomotive Any locomotive featuring two or engines (i.e. cylinders, rods, and wheels) under one boiler, mounted on separate or hinged frames. Permits large locomotives to snake around curves more easily.
Artist Man who is particularly adept, usually with prefix such as brake, pin, speed, etc.
ARU American Railway Union, Crushed during the Pullman strike in 1894.
Ash Cat A locomotive fireman.
Ash Pan A tray under a steam locomotives firebox which accumulates ashes.
Aspect The position or color of lights in a signal.
Association European Rail Association (UIC).
ASTRAC 1) Automatic Simultaneous Train Control (General Electric). 2) [MR] A model railroading system like DCC.
Automatic Block Signal (ABS) A block signal which is activated by track circuit or in conjunction with interlocking or controlled point circuits. This block signal automatically indicates track condition and block occupancy.
Automatic Cab Signal System (ACS) A system which provides for the automatic operation of the cab signals and cab warning whistle.
Automatic Coupler Couplers which will couple and uncouple automatically through the use of uncoupling ramps, permanent or electro-magnets. They permit remote operation as opposed to manual hand methods.
Automatic Stop Arm Mechanical arm located on the RoW linked to a wayside signal. It causes an emergency brake application when a train passes the signal and the arm is in the tripping position.
Automatic Train Control ATC A term covering systems designed to assist the engineer and provide against mishandling or misinterpretation of signals. These systems range from simple cab warning systems to fully automatic control.
Automatic Train Stop System (ATS) A system actuated by wayside inductors, so arranged that its operation will automatically result in the application of the brakes until the train has been brought to a stop.
Auxiliary Tender A second tender; enables an engine to maintain longer runs and reduces intermediate water or fuel stops.
Axle Box A metal casing that houses the axle bearing. Attached to the frame, the axle box transmits the weight of car to the axle.
Axle Counting Counting axles by sensing wheels, with computer control.