page_title: Diesel multiple unit
section_title: United Kingdom
hierarchical_section_title: Diesel multiple unit / Around the world / Europe / United Kingdom
caption_attribution_description: 222009 at St Pancras railway station, London, UK
context_page_description: A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unit railcars are also generally classed as DMUs. Diesel-powered units may be further classified by their transmission type: diesel–mechanical DMMU, diesel–hydraulic DHMU, or diesel–electric DEMU.
context_section_description: 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 and North Eastern Railway and London, Midland and Scottish Railway also experimented with DMUs in the 1930s, the LMS both on its own system, and on that of its Northern Irish subsidiary, but development was curtailed by World War II.
  After nationalisation, British Railways (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 units. The early DMUs proved successful, and under BR's 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, North Eastern and Western regions.
  In 1960, British Railways introduced its Blue Pullman high-speed DEMUs.
  These were few in number and relatively short-lived, 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.
  These 125 mph (201 km/h) trains run with a streamlined power car at each end and (typically) 7 to 9 intermediate trailer cars. 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 Class 43. They remain in widespread use.
  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:
  Class 140–144 Pacer railbuses, ultra-low-cost diesel–mechanical units utilising 4-wheeled chassis and lightweight bus bodywork, designed for provincial branch line and stopping services.
  Sprinter a family of diesel–hydraulic DMUs. These fall into three sub-groups; Class 150 Sprinters (for branch line/commuter service), Class 153 / 155 / 156 Super Sprinters (for longer cross country services), and Class 158 / 159 Express units (for secondary express services);
  Networker diesel–hydraulic units, of Class 165 Network Turbo (standard commuter version) and Class 166 Network Express (for longer distance commuter services). These took over the remaining non-electric commuter services into London.
  Following the impact of the privatisation of British Rail in the late 1990s, several other diesel–hydraulic DMU families have been introduced:
  Class 168 Clubman and Class 170/171/172 Turbostars, a development of the earlier Networkers. These are built by Adtranz and later 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 and ScotRail.
  Class 175 Alstom Coradias were designed by Alstom as a rival to the 170 Turbostar, but bought only by First North Western
  Class 180 Adelantes were an Alstom design for express services built only for Fi
caption: East Midlands Trains Class 222 at London St Pancras
exif: {"Image ImageDescription": "", "Image Make": "SONY", "Image Model": "DSC-N2", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image DateTime": "2009:01:23 16:22:50", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "256", "Image PrintIM": "[80, 114, 105, 110, 116, 73, 77, 0, 48, 51, 48, 48, 0, 0, 2, 0, 2, 0, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail Make": "SONY", "Thumbnail Model": "DSC-N2", "Thumbnail Orientation": "Horizontal (normal)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail DateTime": "2009:01:23 16:22:50", "Thumbnail JPEGInterchangeFormat": "2952", "Thumbnail JPEGInterchangeFormatLength": "17325", "EXIF ExposureTime": "1/200", "EXIF FNumber": "4", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "160", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2009:01:23 16:22:50", "EXIF DateTimeDigitized": "2009:01:23 16:22:50", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "8", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "3", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "137/10", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3648", "EXIF ExifImageLength": "2736", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "2746", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF SceneCaptureType": "Standard", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal"}