Freight multiple unit

A multiple-unit train or simply multiple unit (MU) is a train composed of self-propelled carriages that can be coupled with others of the same or similar type and yet be controlled from one driving cab.

Generally these are passenger trainsets consisting of more than one carriage. Self-sufficient, self-propelled single carriages (also called railcars, rail motor coaches or railbuses) can be regarded as multiple-unit carriages if they are capable of operating in combination with other units.

Multiple units are classified by their power source and are of two main types: electric multiple unit (EMU) or diesel multiple unit (DMU). Diesel-powered units may be further classified by their transmission type: diesel-electric (DEMU), diesel-mechanical (DMMU) or diesel-hydraulic (DHMU).

The term 'multiple unit does not denote locomotives utilising multiple-unit train control.

Multiple-unit train control was first used in Electric Multiple Units in the 1890s. This allowed electrically-powered rapid transit trains to be operated from a single driving position. Early users of such multiple units include the Liverpool Overhead Railway (the first multiple units) and Chicago's South Side Elevated Railroad (the first units to use a low-voltage control system).

The United Kingdom and France (for example Voiture État à 2 étages) had many examples of push-pull steam trains, or autotrains and railmotors on branch lines which include at least partial control of a steam locomotive from a remote cab. These provided many of the operational benefits of a multiple unit, although none incorporated any form of electrical/electronic multiple-unit train control.

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