Locomotive Signaling

an entire system of signaling devices along tracks and in locomotives.

As the train approaches the track signals, the indications of these signals are automatically reproduced on a light signal located in the engineer’s cab of the locomotive. A locomotive signaling system improves traffic safety and increases the traffic-carrying capacity of railroad sections.

Locomotive signaling systems are either point control systems or continuous control systems. For point control systems the communication between the transmitting devices along the track and the receiving devices in the locomotive exists only at certain route points, for instance, before the “home” signals of a station. Such systems are utilized predominantly for train traffic control in sections that have no automatic block system. In continuous locomotive signaling systems the communication between track devices and locomotive devices is maintained everywhere along the route. In such systems the transmitting track devices encode the signal indications of the track light signals. These indications are transmitted through the rail circuit to the locomotive as coded electric signals. Receiver coils in the locomotive sense the magnetic field induced around the rails by the signal current. Signals are decoded by the locomotive decoder and are converted to a display on the cab light signal corresponding to the track signal being approached by the train.

The main railroad lines of the USSR widely use the continuous locomotive signaling system combined with an automatic train stop system (autostop) and speed control system. The autostop system automatically connects an electropneumatic valve and stops the train in the event that an engineer fails to react to the cab signal and does not push the alert lever within 5–7 seconds after an interdicting signal is received. In the speed control system the engineer must reduce train speed down to the speed corresponding to an indication shown on the cab light signal upon approaching an obstacle. If the engineer fails to act in accord with the stated program, the train is stopped automatically.

Future locomotive signaling systems now being developed include automatic train speed control systems combining a multiaspect, continuous signaling system with automatic speed regulation; and a coordinate system of interval control, utilizing inductive loop-shaped communication channels laid along tracks.