Editing Diesel multiple unit (section)

====United Kingdom====
{{further|British railcars and diesel multiple units|List of British Rail diesel multiple unit classes}}
[[File:222009 at St Pancras.jpg|thumb|right|[[East Midlands Trains]] [[British Rail Class 222|Class 222]] at [[St Pancras railway station|London St Pancras]]]]
[[File:170518 at Peterborough.JPG|thumb|[[Central Trains]] [[British Rail Class 170|Class 170]] at [[Peterborough railway station|Peterborough station]]]]
[[File:The 12 - 52 to Londonderry leaves Yorkgate station - geograph.org.uk - 2359652.jpg|thumb|[[Northern Ireland Railways]] [[NIR Class 3000|C3K]] at [[Yorkgate railway station|Yorkgate station]]]]

The first significant use of DMUs in the United Kingdom was by the [[Great Western Railway]], which introduced its small but successful series of diesel–mechanical [[GWR railcars]] in 1934. The [[London & North Eastern Railway]]<ref>{{cite web|url=http://www.lner.info/locos/IC/aw_railcar.php|title=LNER Encyclopedia: The LNER Armstrong-Whitworth Diesel–Electric Railcars|access-date=19 June 2016}}</ref> and [[London, Midland & Scottish Railway]] also experimented with DMUs in the 1930s, the LMS both on [[LMS railcars|its own system]], and on that of its [[Northern Counties Committee#Railcars|Northern Irish subsidiary]], but development was curtailed by [[World War II]].

After nationalisation, [[British Rail]]ways (BR) revived the concept in the early 1950s. At that time there was an urgent need to move away from expensive steam traction which led to many experimental designs using diesel propulsion and [[multiple unit]]s. The early DMUs proved successful, and under BR's [[History of rail transport in Great Britain 1948–1994#The Modernisation Plan|1955 Modernisation Plan]] the building of a large fleet was authorised. These BR "First Generation" DMUs were built between 1956 and 1963.

BR required that contracts for the design and manufacture of new locomotives and rolling stock be split between numerous private firms as well as BR's own workshops, while different BR Regions laid down different specifications. The result was a multitude of different types, one of which was:
* 'Intercity' units, which were more substantially constructed, and shared many features with contemporary hauled coaching stock. They were built for express services on important secondary routes on the [[Scottish Region of British Railways|Scottish]], [[North Eastern Region of British Railways|North Eastern]] and [[Western Region of British Railways|Western]] regions.{{Citation needed|date=July 2012}}

In 1960, British Railways introduced its [[British Rail Classes 251 and 261|Blue Pullman]] high-speed DEMUs.<ref name="Heaps, BR Diary: 1968–1977" >{{cite book |title=BR Diary: 1968–1977 |chapter=End of the Blue Pullmans |last=Heaps |first=Chris |isbn=978-0-7110-1611-8 |year=1988 |publisher=[[Ian Allan Publishing|Ian Allan]] |location=London |pages=66–67 }}</ref>
These were few in number and relatively short-lived,<ref name="Heaps, BR Diary: 1968–1977" /> but they paved the way for the very successful [[InterCity 125]] or High Speed Train (HST) units, which were built between 1975 and 1982 to take over most principal express services on non-electrified routes.<ref>{{cite news |url=http://news.bbc.co.uk/onthisday/hi/dates/stories/october/4/newsid_2486000/2486817.stm |title=1976: New train speeds into service |publisher =BBC News |access-date=15 February 2011 | date=4 October 1976 | location=London}}</ref><ref name=NewOps>{{cite web| url=http://www.railwaysarchive.co.uk/documents/DoT_WP001.pdf |archive-url=https://web.archive.org/web/20071023114338/http://www.railwaysarchive.co.uk/documents/DoT_WP001.pdf |archive-date=2007-10-23 |url-status=live |title=New opportunities for the railways: the privatisation of British Rail |publisher=Railway Archive | page=8 |access-date=15 February 2011 }}</ref>
These {{convert|125|mph|0|abbr=on}} trains run with a streamlined power car at each end and (typically) seven to nine intermediate trailer cars.<ref name="blue253">{{cite web |title=Class 253 High Speed Train |url=http://www.railblue.com/Class%20Headers%20v2.0/class_253V.2.htm |access-date=15 February 2011 |publisher=Railblue.co.uk |archive-date=15 July 2011 |archive-url=https://web.archive.org/web/20110715150731/http://www.railblue.com/Class%20Headers%20v2.0/class_253V.2.htm |url-status=dead }}</ref><ref name="blue254">{{cite web |title=Class 254 High Speed Train |url=http://www.railblue.com/Class%20Headers%20v2.0/class_254V.2.htm |access-date=15 February 2011 |publisher=Railblue.co.uk |archive-date=15 July 2011 |archive-url=https://web.archive.org/web/20110715150736/http://www.railblue.com/Class%20Headers%20v2.0/class_254V.2.htm |url-status=dead }}</ref> Although originally classified as DEMUs, the trailer cars are very similar to loco-hauled stock, and the power cars were later reclassified as locomotives under [[British Rail Class 43 (HST)|Class 43]].<ref name=blue253 /><ref name=blue254 /> HSTs started being replaced in 2017, but as of October 2022 some are still in use.<ref>{{Cite web |title=Great Western Railway calls time on long-distance HSTs |url=https://www.railmagazine.com/news/fleet/great-western-railway-calls-time-on-long-distance-hsts |access-date=2022-10-08 |website=railmagazine.com}}</ref><ref>{{Cite web |title=Final batch of refurbed Inter7City trains handed over to ScotRail |url=https://www.railadvent.co.uk/2021/03/final-batch-of-refurbed-inter7city-trains-handed-over-to-scotrail.html |access-date=2022-10-08 |website=RailAdvent |date=13 March 2021}}</ref>

By the early 1980s, many of the surviving First Generation units were reaching the end of their design life, leading to spiralling maintenance costs, poor reliability and a poor public image for the railway. A stopgap solution was to convert some services back to locomotive haulage, as spare locomotives and hauled coaching stock were available, but this also increased operating costs. Commencing in the mid '80s, British Rail embarked upon its so called "Sprinterisation" programme, to replace most of the first generation DMUs and many locomotive-hauled trains with three new families of DMU:
*[[Pacer (British Rail)|Class 140–144 ''Pacer'']] [[railbus]]es, ultra-low-cost diesel–mechanical units (later converted to hydraulic) utilising four-wheeled chassis and lightweight bus bodywork, designed for provincial branch line and stopping services.
*[[Sprinter (British Rail)|Sprinter]] a family of diesel–hydraulic DMUs. These fall into three sub-groups; [[British Rail Class 150|Class 150]] ''Sprinters'' (for branch line/commuter service), [[British Rail Class 153|Class 153]] / [[British Rail Class 155|155]] / [[British Rail Class 156|156]] ''Super Sprinters'' (for longer cross country services), and [[British Rail Class 158|Class 158]] / [[British Rail Class 159|159]] ''Express'' units (for secondary express services);
*[[Networker (train)|Networker]] diesel–hydraulic units, of [[British Rail Class 165|Class 165]] ''Network Turbo'' (standard commuter version) and [[British Rail Class 166|Class 166]] ''Network Express'' (for longer distance commuter services). These took over the remaining non-electric commuter services into London.{{Citation needed|date=July 2012}}

Following the [[impact of the privatisation of British Rail]] in the late 1990s, several other DMU families have been introduced:{{Citation needed|date=February 2012}}
* [[British Rail Class 168|Class 168]] ''Clubman'' and [[British Rail Class 170|Class 170]]/[[British Rail Class 171|171]]/[[British Rail Class 172|172]] [[Bombardier Turbostar|Bombardier ''Turbostar'']], a development of the earlier ''Networkers''. These are built by [[Adtranz]] and later [[Bombardier Transportation|Bombardier]] at [[Derby Litchurch Lane Works]] and are the most numerous and widespread of the post-privatisation designs. Purchased by [[Anglia Railways]], [[Central Trains]], [[Chiltern Railways]], [[London Midland]], [[London Overground Rail Operations]], [[Midland Mainline (train operating company)|Midland Mainline]] and [[ScotRail (National Express)|ScotRail]]. All are diesel-hydraulic except for the Class 172, which is diesel-mechanical.
*[[British Rail Class 175|Class 175]] [[Alstom Coradia|Alstom ''Coradia'']] diesel-hydraulic multiple units were designed by [[Alstom]] as a rival to the 170 Turbostar, but bought only by [[First North Western]]
*[[British Rail class 180|Class 180]] ''Adelante'' diesel-hydraulic multiple units were an Alstom design for express services built only for [[First Great Western]]
*[[British Rail Class 185|Class 185]] [[Siemens Desiro|Siemens ''Desiro'']], built by [[Siemens Mobility|Siemens]] introduced in 2006 by [[First TransPennine Express]]
*[[British Rail Class 195|Class 195]]/[[British Rail Class 196|196]]/[[British Rail Class 197|197]] [[CAF Civity|CAF ''Civity'']], built by [[Construcciones y Auxiliar de Ferrocarriles|CAF]] for [[Arriva Rail North]], [[West Midlands Trains]] and [[Transport for Wales Rail|Transport for Wales]]
*[[British Rail Class 220|Class 220]]/[[British Rail Class 221|221]]/[[British Rail Class 222|222]] ''[[Bombardier Voyager|Voyagers/Meridian]]'' diesel-electric multiple units built by Bombardier in [[Bruges]] for [[Hull Trains]], Midland Mainline and [[Virgin CrossCountry]]

In 2018, the first [[Electro-diesel multiple unit|bi and tri-mode electro-diesel multiple units]] were introduced:
*[[British Rail Class 800|Class 800]]/[[British Rail Class 802|802s]] are being built by [[Hitachi]] for [[Great Western Railway (train operating company)|Great Western Railway]], Hull Trains, [[London North Eastern Railway]] and [[TransPennine Express]]<ref>[http://www.railwaygazette.com/news/traction-rolling-stock/single-view/view/gwr-unveils-hitachi-iep-trainset.html GWR unveils Hitachi iep trainset] {{Webarchive|url=https://web.archive.org/web/20180425131316/http://www.railwaygazette.com/news/traction-rolling-stock/single-view/view/gwr-unveils-hitachi-iep-trainset.html |date=25 April 2018 }} ''[[Railway Gazette International]]'' 30 June 2016</ref>
*[[British Rail Class 755|Class 755]] [[Stadler FLIRT|Stadler ''FLIRT'']] are to be operated by [[Abellio Greater Anglia]]<ref>[http://www.railwaygazette.com/news/passenger/single-view/view/stadler-and-bombardier-to-supply-trains-for-abellio-east-anglia-franchise.html Stadler and Bombardier to supply trains for Abellio East Anglia franchise] ''Railway Gazette International'' 10 August 2016</ref>
*[[British Rail Class 769|Class 769s]] are being converted by [[Brush Traction]] from [[British Rail Class 319|Class 319s]] for Arriva Rail North, Great Western Railway and [[KeolisAmey Wales]]<ref>[http://www.railwaygazette.com/news/traction-rolling-stock/single-view/view/gwr-to-lease-class-769-flex-trimode-trainsets.html GWR to lease Class 769 Flex trimode trainsets] {{Webarchive|url=https://web.archive.org/web/20180727201324/http://www.railwaygazette.com/news/traction-rolling-stock/single-view/view/gwr-to-lease-class-769-flex-trimode-trainsets.html |date=27 July 2018 }} ''Railway Gazette International'' 20 April 2018</ref>
*[[British Rail Class 230|Class 230s]] were converted by [[Vivarail]] from [[London Underground D78 Stock]]<ref>{{cite web|url=http://www.railtechnologymagazine.com/Interviews/they-dont-make-trains-like-this-anymore|title='They don't make trains like this anymore'|website=railtechnologymagazine.com|access-date=2019-07-18}}</ref> for [[West Midlands Trains|West Midland Trains]]<ref>{{cite web|url=https://www.railway-technology.com/news/west-midlands-trains-puts-first-class-230-d-train-in-service/|title=West Midlands Trains puts first Class 230 D Train in service|date=2019-04-23|website=Railway Technology|access-date=2019-07-18}}</ref> and [[Transport for Wales Rail|Transport for Wales]].<ref>{{cite web|url=https://www.dailypost.co.uk/business/business-news/new-north-wales-trains-slower-15116084|title=New North Wales trains will be slower than Arriva ones BUT journey times will fall|last=Hughes|first=Owen|date=2018-09-10|website=northwales|access-date=2019-07-18}}</ref> After the collapse of Vivarail in 2022, the West Midlands units were withdrawn from service.<ref>{{cite news |last1=Dobell |first1=Malcolm |title=Class 150 units back on the Marston Vale line |url=https://www.railengineer.co.uk/class-150-units-back-on-the-marston-vale-line/ |access-date=11 August 2024 |work=Rail Engineer |date=19 December 2023}}</ref>