' is a term used to describe a train which does not have a separate locomotive. Typically these are passenger trains with accommodation in every vehicle and motors or engines distributed under the floor along the length of the train. The term is further classified by the method of propulsion: Diesel (DMU
), Electric (EMU
) or Diesel-Electric (DEMU
The term is also used, more loosely, to describe a train such as the Advanced Passenger Train
which was a permanent formation with 'power cars' in the train rather than a locomotive at one end.
This article describes the history, development and current use of diesel and electric multiple units in Great Britain.
Prior to the Nationalisation that formed British Railways
in 1948, all of the Big Four
railway companies (GWR, LMS, LNER, SR) had experimented with using multiple units to some extent.
The Southern Railway
went much further, implementing an extensive programme of electrification on its commuter routes, and consequently was a large user of EMUs.
Multiple unit operation on suburban routes was also (by Nationalisation) in use in London, the extensive operations of the LSWR
(later part of the Southern) being the most visible example. Multiple unit operation was also in use on some suburban routes of the LMS in London
, Manchester and on Merseyside (Mersey Railway
). The LNER was also using electric units on Tyneside
Alongside the mainline railways, urban transit system
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