Railway Signaling and Operations

Railroad Terminology

• An Absolute Block is a block that cannot be occupied by more than one train at a time.
• An "A" Car is a rail car equipped with an Engineer's cab.

Tracks

• Adjacent Tracks are two or more tracks with track centerlines spaced less than 25 feet apart.
• Adjacent Controlled Tracks are controlled tracks with track centers spaced 19 feet or less from the occupied track.

Signaling

• An Aspect is the appearance of a fixed signal viewed from the direction of an approaching train (e.g. green light).
• An Automatic Block Signal System is a series of track sections governed by block signals actuated by trains, controlling the spacing of trains.
• Automatic Block Signals are fixed signals at the entrance of a block or track section, governing the movement of approaching trains, identified by a number and the letter Z or D.

Train Control Systems

• Automatic Train Control (ATC) is a system to enforce compliance with cab and wayside signal indications.
• Automatic Train Operation (ATO) is a system where carborne equipment operates the train to and from stations, and opens and closes the doors, supervised by the Conductor and the Train Engineer.
• An Automatic Train Stop is a device that causes a full emergency application of the brakes if a train fails to stop prior to a signal indicating STOP.

Track Infrastructure

• Ballast is sized rock or concrete placed on the roadbed to support the track structure, ties, and rail, and to hold the track in line and surface.

Train Operations

• A Block is a length of track of defined limits, governed by block signals or verbal block indication.
• Bridging occurs when a rail car becomes a conducting element between an energized section and a de-energized section of Third Rail.
• A "C" Car is a rail car without an Engineer's cab.
• Clearance is the suitable amount of space or distance required to allow a train or other vehicle to pass without obstruction.
• A Collector Train is a train operated without customers for the collection of revenue at stations.
• A Consist is two or more cars coupled together to make up a train.
• A Contact Shoe is a device that conducts electrical current from the Third Rail to the railcar.
• The Control Center is the central location from which PATH operations are controlled.