Railroad Legal Glossary: A

AB Valve: The operating device used on freight cars for charging, applying, and releasing the brakes. Also called a triple valve.

ABD Valve: An improvement of the AB Value that features a quick release. 

ABDW Valve: An improvement of the ABD Valve. Modifies the Emergency Portion and provides for accelerated buildup of brake cylinder pressure during quick service applications. 

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: 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" market or the absence of a number plate. 

Add: Couple car(s) to a train. 

Affidavit: A written statement under oath. 

Agreement: Mutual assent between two or more parties; normally leads to a contract; may be verbal or written.

Air Brake System: All of the devices and parts included in making an air brake for controlling the speed and stopping a locomotive or train. It is made up of the operating devices, the pipes, fittings and foundation brake gear. 

Alley: A clear track in a switching yard. 

Angle Cock: An appliance 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. 

Answer: Pleading filed by the defendant that responds to a complaint, petition, or motion.

Appeal: A request to the higher court for review of the lower court?s decision and to request a reversal of the judgment.

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. 

Arbitration: The procedure by which a dispute may be resolved by a person who is not a judge.  Arbitration is often used to limit legal costs to both parties.

Arbitrator: A person who conducts an arbitration.

ARU: American Railway Union.

Assumption of Risk: A doctrine that states if the plaintiff has knowingly accepted the danger of doing something, recovery from the defendant in an action brought for negligence will be barred.

Automatic Block Signal System: A series of consecutive blocks governed by block signals, cab signals or both, actuated by a train, engine or by certain conditions affecting the use of a block. 

Automatic Cab Signal System: A system which provides for the automatic operation of the cab signals and cab warning whistle. 

Automatic Train Stop System: 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.