Multiple-unit train control

Transporting multi-engine vehicles, for example locomotives, together a train, this is called multiple. In this case, all these vehicles run regularly on the train and be remotely controlled centrally from the first vehicle using a multiple control; which is a body set up by connecting cable remote control from the cab at the front to the rear drive vehicle. The simplest multi-traction is the double header, thus driving with two locomotives at one end of the train or the coupling of two trainsets (see also outflanking ). Similarly, there are triple traction, four -unit, etc.; locomotives, the tensile strength of the coupling to the first carriage limits the possible train number.


Be distinguished from multiple traction are:

  • Multiple locomotives (eg double locomotives) and members of multiple units, in which a single train of several ( short ) coupled units, which are operationally not or only rarely separable
  • Bias, in which a train is additionally tensioned front of a train without a remote control connection
  • Subsequent pushing, where a train is temporarily pushed from one additional train, that's not remotely, possibly not even coupled to the train.
  • Wagenlok when a non-working drive vehicle is provided for the transfer " as a car" on the train, in addition to motive power. - In a way, the functional inverse of a Lokzugs.

In railcars and multiple units a coupling vehicles to organizations is only possible when multiple traction without loss of performance. For wagons trains, especially in freight transport more than one train is often necessary to transport heavy trains on certain routes at all.

Special forms


The locomotive sandwich (less than tandem, referred to in Switzerland as Doppelpendelzug ), ie driving with two locomotives at opposite ends of a wagon train that differs from the double traction through reduced clutch load and Wendezugfähigkeit without the need of a control car. With cable remote control, the car must here, however, offer the possibility of coupling through the control line.

Distributed traction

In distributed traction locomotives or locomotive groups run not only at the ends, but also in the middle of a wagon train. This makes it possible to bring greater tensile forces on a train without overstressing the couplings.

In Central and Western Europe no multiple unit forms except the simple double traction for freight are common practice; passenger however come a long drive sidecars (eg, five units) before.

Elsewhere, especially in the U.S., reign long freight trains still powered by diesel traction. The high gross combination weights require multiple, distributed traction ( "distribution traction ", see also " Distributed Power Unit" ). Up to eight locomotives per train may occur, thereby allowing the high strength of Janney couplings used in the United States the use of up to four six-axle locomotives on the Zugspitze.

A-unit and unit B

In the United States führerstand loose diesel locomotives were designed for hauling heavy freight trains in multiple traction, which was called the B-unit or as a booster. These were controlled by an A-unit, ie a locomotive with a driving cab from.

Guided motor coach at the tram

Chance exist so-called Beitriebwagen in the tram area. These are motorized, but do not have a ( full ) driver's cab and therefore can not run in the first place a consist.

Types of control

In the steam locomotive era, there were no multiple traction in the modern sense, but really only preload and subsequent pushing; all locomotives were staffed and were controlled individually, the communication was made by whistle signals.

In Europe, locomotives are now generally controlled via line connections; thereby communicate the control computer of the vehicles via bus cable, which must be led by the middle car. Sometimes only identical vehicles are traction capability with each other. In Germany and Switzerland, many locomotives and driving coaches can be with each other a lot of times controlled. See also: multiple unit control.

Etc. The distributed traction in the U.S. would actually require a control line, as it is often provided in European high-speed freight cars already for the electro-pneumatic brake. This is at least in the U.S., but not common, so that the traction control is carried out by radio.