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.
The British Rail Class 108 diesel multiple units were built by BR Derby from 1958 to 1961, with a final production quantity of 333 vehicles.
The British Rail Class 121 is a single-car double-ended diesel multiple unit. 16 driving motor vehicles were built from 1960, numbered 55020–55035. These were supplemented by ten single-ended trailer vehicles, numbered 56280–56289. They have a top speed of 70 mph, with slam-doors, and vacuum brakes. The driving motor vehicles were nicknamed "Bubble Cars" by some enthusiasts.
The British Rail Class 122 diesel mechanical multiple units were built by Gloucester RC&W in 1958. Twenty single-car, double-ended driving motor vehicles, nicknamed "Bubble Cars", were built, numbered 55000–55019. These were supplemented by nine single-ended trailer vehicles, numbered 56291–56299.
The British Rail Class 116 diesel multiple units were built by BR Derby from 1957 to 1961. Introduced as part of the British Railways Modernisation Plan in the mid 1950s, as with other first generation DMUs the 116 was intended to replace steam trains and reduce costs across the rail network. Alongside Metro-Cammell, BR Derby had prior experience with DMUs, having developed a Lightweight Unit, and so was awarded a contract for a new design.
The British Rail Class 104 diesel multiple units were built by Birmingham Railway Carriage and Wagon Company from 1957 to 1959.
The British Rail Classes 101 and 102 diesel-mechanical multiple units were built by Metro-Cammell at Washwood Heath in Birmingham, England from 1956 to 1959, following construction of a series of prototype units. These classes proved to be some of the most successful and longest-lived of BR's First Generation DMUs, second in longevity only to the Class 121, with the final five units being withdrawn on 24 December 2003. The oldest set was, by then, just over 47 years old.
The British Rail Class 127 diesel multiple units were built by BR Derby in 1959. Thirty 4-car units were built, formed of two outer driving motor vehicles, sandwiching two intermediate trailers which were classified class 186. The technical description of such as 4-car unit was DMBS + TSL + TS + DMBS.
The British Rail Class 144Pacer is a diesel multiple unit (DMU) passenger train built at Derby between 1986 and 1987. British Rail, seeking to procure improved derivatives of the earlier Class 141, placed an order with the manufacturers British Rail Engineering Limited (BREL) and Walter Alexander to construct their own variant, the Class 144. A total of 23 units were constructed. All units have now retired from mainline service, though the majority of the units have been acquired for preservation on heritage railways and in other uses. As of December 2022, 19 out of the 23 units have been purchased following withdrawal for this purpose, of which 14 units are in operational condition.
The British Rail Class 118 diesel multiple units were built by the Birmingham Railway Carriage and Wagon Company (BRCW) and introduced from 1960. It was a licence-built version of the British Rail Class 116.
The Endeavour Railcars are a class of diesel multiple units operated by NSW TrainLink on passenger rail services in New South Wales, Australia on the Hunter, Blue Mountains, Southern Highlands and South Coast lines. They are mechanically identical to the Xplorers. All 30 carriages were built by ABB's Dandenong rolling stock factory.
The British Rail Class 155 is a diesel multiple unit passenger train. These DMUs were built by Leyland Bus at Workington between 1987 and 1988 as part of BR's replacement of its ageing first-generation diesel fleet. 42 units were originally built, of which only 7 remain; the other 35 units were converted to Class 153 railcars.
The British Rail Classes 105 and 106 diesel multiple units were built by Cravens Ltd. of Sheffield from 1956 to 1959. The class were built with a side profile identical to British Railways Mark 1 carriage stock, using the same doors and windows. None were selected for refurbishment. The last passenger car was withdrawn from service in 1988.
The British Rail Class 107 diesel multiple units were built by the Derby Works of British Railways and were introduced in 1960. The class looked similar to the later Class 108 units, but were heavier, being built from steel.
The British Rail Class 115 diesel multiple units were 41 high-density sets which operated the outer-suburban services from Marylebone usually to destinations such as High Wycombe, Aylesbury and Banbury which are on the Chiltern Main Line and Great Central Main Line. Sometimes, these sets used to operate 8- or 12-car-long expresses to Nottingham Victoria in the final years of the GCML. Coincidentally, Class 115 units operated services under Table 115 in the British Rail timetable.
The British Rail Class 210 was a type of diesel-electric multiple unit (DEMU) passenger train designed and constructed by British Rail Engineering Limited's Derby Litchurch Lane Works.
The British Rail Class 120 was a cross-country DMU in three-car formation, built at the British Rail Swindon Works.
The British RailClass 141 is the first production model of the Pacer diesel multiple unit (DMU) railbus.
The 450 Class is a type of diesel multiple unit (DMU) passenger train formerly used by Northern Ireland Railways. They were affectionately nicknamed 'Thumpers' and 'Castles' by rail enthusiasts.
Diesel multiple units and railcars are trains, usually with passenger accommodation, that do not require a locomotive. Railcars can be single cars, while in multiple units cars are marshalled together with a driving position either end. As of December 2010, 23 percent of the rail passenger cars used on Network Rail are part of a diesel multiple unit.
