Abstract: A method is provided for detecting broken rail, unintentionally misaligned turnouts, and track occupancy ahead of or behind a railway vehicle traveling on a railroad track. Shunts extend between the rails at intervals along the railroad track. Each shunt has electrical signal transmission characteristics differing from those of adjacent shunts. A test unit on the railway vehicle induces a test signal in a first rail to create a track circuit in which the test signal propagates along the first rail, through at least one of the shunts, returns to the railway vehicle along the second rail, and through the wheels and axle of the railway vehicle. The test signal has electrical properties selected to interact with at least one of the shunts. The received test signal on the second rail is analyzed to identify predetermined conditions concerning the status of the railroad track.

Abstract: A method is provided for detecting broken rail, track continuity, and track occupancy ahead of or behind a railroad vehicle traveling in fixed-block territory equipped with an AC track code wayside signal system or cab signal overlay system, and a communications link. This method, when used as an integral part of a communications-based train control (CBTC) or positive train control (PTC) system, allows immediate, automatic detection of broken rail, track occupancies, or open turnouts ahead of or behind a train in an occupied block. It also facilitates true moving-block or virtual block CBTC or PTC, thereby enabling higher efficiency and track utilization.

Abstract: A method is provided for detecting broken rail, track continuity, and track occupancy ahead of or behind a railroad vehicle traveling in fixed-block territory equipped with an AC track code wayside signal system or cab signal overlay system, and a communications link. This method, when used as an integral part of a communications-based train control (CBTC) or positive train control (PTC) system, allows immediate, automatic detection of broken rail, track occupancies, or open turnouts ahead of or behind a train in an occupied block. It also facilitates true moving-block or virtual block CBTC or PTC, thereby enabling higher efficiency and track utilization.

Abstract: A method is provided for detecting broken rail, unintentionally misaligned turnouts, and track occupancy ahead of or behind a railway vehicle traveling on a railroad track. Shunts extend between the rails at intervals along the railroad track. Each shunt has electrical signal transmission characteristics differing from those of adjacent shunts. A test unit on the railway vehicle induces a test signal in a first rail to create a track circuit in which the test signal propagates along the first rail, through at least one of the shunts, returns to the railway vehicle along the second rail, and through the wheels and axle of the railway vehicle. The test signal has electrical properties selected to interact with at least one of the shunts. The received test signal on the second rail is analyzed to identify predetermined conditions concerning the status of the railroad track.