Cab car

A control car, control trailer or driving trailer is a generic term for a non-powered railroad (US) or railway (UIC) vehicle that can control operation of a train from the end opposite to the position of the locomotive. They can be used with Diesel or electric motive power, allowing push-pull operation without the use of an additional locomotive. They can also be used with a power car or a railcar. In a few cases control cars were used with steam locomotives, especially in Germany and France (see article Voiture État à 2 étages).

In the United States, cab cars are control cars similar to regular passenger car, but with a full driver's compartment built into one or both ends. They can be very similar to regular rail cars, to the point of including a gangway between cars so that they could be used in the middle of a passenger train like a regular car if necessary. European railways have used such equipment since the 1920s. In the United States they appeared for the first time in the 1960s. In the United Kingdom, driving trailers may have one or two driving cabs.

Trains operating with a locomotive at one end and a control car at the other do not require the locomotive to run around to the opposite end of the train when reversing direction at a terminus. Control cars can carry passengers, baggage, mail or a combination thereof, and may, when used together with Diesel locomotives, contain an engine-generator set to provide head-end power (HEP).

In addition to the driver's cab, which has all the controls and gauges necessary for remotely operating the locomotive, control cars usually have a horn, whistle, bell, or plough (as appropriate), and all of the lights that would normally be on a locomotive. They must also be fitted with all necessary communication and safety systems like GSM-R or European Train Control System (ETCS).

The classic control method was a multiple unit cable with jumpers between cars. In North America and Ireland a standard AAR 27-wire cable is used, in other countries cables with up to 61 wires can be found. A more recent method is to control the train through a Time-Division Multiplexed (TDM) connection, which usually works with two (protected) wires.

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