A JNR Class KiHa40 in use for Erimo Express service, Hokkaido, Japan
An IE 29000 Class diesel multiple unit on a western commuter service at Dublin Connolly Rail station, Ireland
A British Rail Class 185 diesel hydraulic multiple unit operated by TransPennine Express at Manchester Piccadilly station, United Kingdom

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 diesel engine may be located above the frame in an engine bay or under the floor. Driving controls can be at both ends, on one end, or in a separate car.

Types by transmission

DMUs are usually classified by the method of transmitting motive power to their wheels.[citation needed]


In a diesel–mechanical multiple unit (DMMU), the rotating energy of the engine is transmitted via a gearbox and driveshaft directly to the wheels of the train, like a car. The transmissions can be shifted manually by the driver, as in the great majority of first-generation British Rail DMUs, but in most applications, gears are changed automatically.


One of the underfloor diesel engines with hydraulic transmission under a car of JR Shikoku 2700 series DMU

In a diesel–hydraulic multiple unit (DHMU), a hydraulic torque converter, a type of fluid coupling, acts as the transmission medium for the motive power of the diesel engine to turn the wheels. Some units feature a hybrid mix of hydraulic and mechanical transmissions, usually reverting to the latter at higher operating speeds as this decreases engine RPM and noise.


"Power Pack" car of Stadler FLIRT DMU with open bay of a diesel-generator. The Jacobs bogies under this car do not have their own traction motors, which are mounted on bogies under other cars.

In a diesel–electric multiple unit (DEMU), a diesel engine drives an electrical generator or an alternator which produces electrical energy. The generated current is then fed to electric traction motors on the wheels or bogies in the same way as a conventional diesel–electric locomotive.[1]

On some DEMUs, such as the Bombardier Voyager, each car is entirely self-contained and has its own engine, generator and electric motors.[1] In other designs, such as the British Rail Class 207 or the Stadler GTW and Stadler FLIRT DMU,[2] some cars within the consist may be entirely unpowered or only feature electric motors, obtaining electric current from other cars in the consist which have a generator and engine.

With diesel–electric transmission, some DMU can be no other than an EMU without pantograph or contact shoes (for use on the former British Rail Southern Region), which "is substituted" by one or more on-board diesel generators; this kind of DEMU can be potentially upgraded to electro-diesel multiple unit (EDMU), becoming a bi-mode multiple units train (BMU), just adding one or two pantographs or contact shoes (with opportune converters,[clarification needed] if necessary) and related modifications on the electric system.[citation needed]

Around the world



NMBS/SNCB uses its NMBS/SNCB Class 41 DMUs on the few remaining unelectrified lines. As electrification progresses, the DMUs become less and less important.


DMU 7023 at Zagreb Central Station

Diesel multiple units cover large number of passenger lines in Croatia which are operated by the national passenger service operator HŽ Putnički Prijevoz. On Croatian Railways, DMUs have important role since they cover local, regional and distant lines all across the country. The country's two largest towns, Zagreb and Split, are connected with an inter-city service that is provided by DMU tilting trains "RegioSwinger" (Croatian series 7123) since 2004. Those trains may also cover other lines in the country depending on need and availability.

Luxury DMU series 7021, built in France, started to operate for Yugoslav Railways in 1972 and after 1991 still remained in service of Croatian Railways until 2005. Units 7121 and 7122 (which came as a replacement for 7221 units), together with the newest series 7022 and 7023 built in 2010s Croatia, cover many of the country's local and regional services on unelectrified or partly electrified lines.

Czech Republic

ČD Class 810
ČD Class 814

Diesel multiple units also cover large number of passenger lines in the Czech Republic which are operated by the national operator České dráhy. They have important role since they cover local, regional and distant lines all across the country. Those trains may also cover other lines in the country depending on need and availability too.

Also, the DMUs were manufactured for foreign carriers. The tables of cars and units are divided into vehicles operated until 1987, when the ČSD used the series designations proposed by Vojtěch Kryšpín, and vehicles created after this date, which no longer have Kryšpín's designations (with some exceptions). In addition, these new cars are the new vehicles are already different in both countries.


Elron has since 2015 a Stadler FLIRT fleet, with 20 trains DEMU version.


Germany has employed DMUs for both commuter and express services for many decades. The SVT 877 Fliegender Hamburger DMU, introduced in 1933, made the run from Berlin to Hamburg in an astonishing 138 minutes, and its derivative SVT 137 broke the land speed record in 1936. After World War 2, the VT 11.5 DMU was the flagship of the glamorous Trans Europ Express.

Since 1968, DB has designated DMUs with class numbers beginning in 6. While DB and regional transport authorities generally prefer electric power for commuter rail, many local and rural lines remain un-electrified, and DMUs are invaluable in providing services to those areas. DMUs in service as of 2021 include the Adtranz Class 612 tilting train ("Regio Swinger"), the Alstom Coradia LINT (Classes 620–623, 640 and 648), the Siemens Desiro (Class 642) and the Bombardier Talent (Class 643/644). From 2001 to 2016 there was even a DMU version of DB's high-speed Intercity Express, the Class 605 ICE TD.



Main article: Multiple units of Ireland

Iarnród Éireann DMU 2751 at Limerick Colbert station, 2006

In the Republic of Ireland the Córas Iompair Éireann (CIÉ), which controlled the republic's railways between 1945 and 1986, introduced DMUs in the mid-1950s and they were the first diesel trains on many main lines.[3][citation needed]


Romanian Class 77 Malaxa DMU in Câmpulung Moldovenesc in 2006

DMUs are used mostly on shorter or less frequently travelled routes in remote areas. The national railway company CFR still uses, along with other DMU models, Class 77 and 78 DMUs, locally built by Malaxa between the 1930s and 50s and refurbished in the 70s. The main DMU in use is the Class 96 Siemens Desiro aka Săgeata Albastră (The Blue Arrow). Private operators also largely use DMU units, mainly purchased from various French and German operators.


ZSSK Class 813

In the present, several types of DMUs operate in Slovakia. Was the most common type in Slovakia is a Class 812 ZSSK based on the ČD Class 810. These are used almost exclusively for hauling passenger trains on non-electrified regional lines and these trains often excel in low travel speeds. In the past, however, in Slovakia there were a number of express trains driven by motor coaches, which often overcame heavier trains driven by steam locomotives at cruising speed, and classic sets. A typical example can be, for example, the Slovenská strela motor express train led on the Bratislava-Prague route by a motor car of the same name, or the Tatran express from Bratislava to Košice. Representatives of high-speed motor wagons were, for example, motor wagons of the M262 or M286 series, which, however, lost their application in high-speed wagons due to the gradual electrification of main lines and were, like the current wagons currently used for passenger trains.

United Kingdom

Further information: British railcars and diesel multiple units and List of British Rail diesel multiple unit classes

East Midlands Trains Class 222 at London St Pancras
Central Trains Class 170 at Peterborough station
Northern Ireland Railways C3K at 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[4] and London, Midland & 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:

In 1960, British Railways introduced its Blue Pullman high-speed DEMUs.[5] These were few in number and relatively short-lived,[5] 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.[6][7] These 125 mph (201 km/h) trains run with a streamlined power car at each end and (typically) seven to nine intermediate trailer cars.[8][9] 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.[8][9] HSTs started being replaced in 2017, but as of October 2022 some are still in use.[10][11]

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:

Following the impact of the privatisation of British Rail in the late 1990s, several other diesel–hydraulic DMU families have been introduced:[citation needed]

In 2018, the first bi and tri-mode electro-diesel multiple units were introduced:

North America


Two Bombardier Talent low-floor DMUs on the O-Train Trillium Line in Ottawa, Canada

Canada generally follows similar buffer strength requirements to the US,[18] but new services are evaluated on a case-by-case basis. As a result, several types of lightweight DMUs have been used:

Costa Rica

Apollo 2400 DMU in service in Costa Rica

Costa Rica has purchased several Apolo 2400 series DMU railcars from the former narrow gauge operator in Spain, which are run in commuter service.[20]


42 X'Trapolis Tsíimin K'áak train sets have been ordered for Tren Maya, 10 of which are DMU and 32 are EDMU.[21]

United States

Budd Rail Diesel Car RDC-1 #407 of the Cape May Seashore Lines, New Jersey

A type of diesel multiple units in the U.S. was the Budd Rail Diesel Car (RDC). The RDC was a single passenger car with two diesel engines and two sets of controls.[22]

In the United States, DMU systems must be FRA-compliant to be permitted on freight rail corridors. The Federal Railway Administration has mandated higher coupling strength requirements than European regulators, effectively prohibiting the use of lighter weight European-style inter-city rail DMUs on U.S. main line railways without timesharing with freight operations or special waivers from the FRA. This has greatly restricted the development of DMUs within the U.S. as no other country requires the much heavier FRA compliant vehicles, and no export market for them exists.[23]

FRA compliant Colorado Railcar DMU of WES Commuter Rail.

Operations using FRA-compliant vehicles:

Operations using non FRA-compliant vehicles:

Stadler FLIRT owned by TEXRail in Texas

Proposed operations:



A V/Line VLocity operating in Victoria, Australia

DMUs were first introduced to Australia in the late mid-20th century for use on quiet branch lines that could not justify a locomotive hauled service. Today, DMUs are widely used throughout Australia's southern states:

In Queensland, heritage DMUs are used on the Savannahlander and Gulflander tourist trains.


Chinese manufactured (CNR Tangshan) DEMU was introduced in Bangladesh from 25 May 2013. DEMU is the country's first-ever commuter train service starting its journey on the Chittagong–Fouzdarhat line. These DEMUs also operate on the Chittagong Circular Railway and on the Bangladesh Railway's service between Dhaka and Narayanganj.[35]

A DEMU train (right) at Kamalapur railway station, Dhaka


Mexican manufacturer Ferrovias Del Bajio supplied in 2019, three DSUs (Diesel Single Unit) to Royal Railway in Cambodia for their airport shuttle service from Phnom Penh international airport to the city central station. The other two units were assigned to long-distance services from the central station to Sihanoukville and to Poipet. Royal Railways Cambodia have now acquired eleven carriages DMU from Japan. Model: “ Kiha 183 heavy snow “. (キハ183系オホーツク・大雪) Speed: 110 km/h (max) Type: 特急 (Limited Express) Started: 1986 ............ End of Service in Japan 17 March 2023

Ferrovias del Bajio DSU at Phom Penh Cambodia Airport


DMUs (DEMUs) are widely used in India. DEMUs in India are used in both the eight-coach format and the four-coach format. These trains replaced many (up to 10 car) trains with a WDM-2 or WDM-3A locomotive in the middle. These old trains had the loco controls duplicated in the Driving Trailer coach and all the actuation information reaching the locomotive through thin communication lines. This was called 'push-pull train'. The longest running such push-pull service operated between Diva – Bhiwandi Road and Vasai Road and was recently converted into an MEMU train service in 2018.

India's first and largest DMU shed at Jalandhar, Punjab, holds more than 90 units placed in service all over Punjab. First generation DMU: Rated power was 700 HP and had three or six coaches, made first by ICF. Transmission was Voith-hydraulic. Max speed 100 km/h.

Second generation DMU: Rated power is 1400 HP and have eight coaches. Max speed is 105 km/h. Transmission is DC electric. Made at ICF and RCF.

Third generation DMU: Rated power is 1,600 HP and have ten coaches. Max speed is 110 km/h. Transmission is AC electric. Made at ICF.


KRDI Solo Express, Surakarta

State-owned company PT.INKA builds several type of DMU, some of which operate in urban and suburban areas.


JR Hokkaido KiHa 283 tilting DMU on Hakodate Main Line

In Japan, where gasoline-driven railbuses (on small private lines) and railmotors (Kihani 5000 of the national railways) had been built since the 1920s, the first two streamlined DMUs came in service in 1937, class Kiha 43000 (キハ43000系).[36]

The service of several hundreds (in sum even thousands) of diesel railcars and DMUs started in 1950s following the improvement of fuel supply that was critical during World War II.[37]


In 2021, Kenya acquired DMUs from France to operate in the Nairobi Metropolitan Area. These trains connect the city with settlements outside Nairobi, Jomo Kenyatta International Airport and the Nairobi Terminus.


The Keretapi Tanah Melayu (KTM) has a total of 13 DMU KTM Class 61 ordered from CRRC for the West Coast Line and are assembled locally at CRRCs Batu Gajah factory from 2016 to 2020. The first scheduled service is expected from 1 September along the Gemas-Johor Bahru route, replacing old non-automotive stock.[38]


The Philippine National Railways (PNR) was one of the first adopters of diesel multiple unit trains in Asia. Initially built as gasoline-powered railmotors, the locally assembled Manila Railroad RMC class of 1929 was the first to be powered by diesel traction. Some units were also converted to streamliner units by 1932 for first-class services on the South Main Line between Manila and Legazpi, Albay.[39] Since then, generations of DMUs were used chiefly for short-distance commuter services by the PNR in the island of Luzon.[40][41]

Even without active inter-city rail services in the present-day, DMUs are still used on the PNR Metro Commuter Line in Metro Manila and the Bicol Commuter service in the Bicol Region.[42] Three generations of DMUs are in use: second-hand DMUs handed over by JR East such as the KiHa 35, 52 and 59 series originally built in the 1960s and acquired in the early 2010s,[43][44] the Rotem DMUs of 2009 built by Korean manufacturer Hyundai Rotem,[45] and the 8000 and 8100 classes built by Indonesian firm PT INKA.[46][47]

From 2022 onwards, the PNR will purchase standard gauge DMUs for its upcoming inter-city rail network in Luzon and Mindanao. This is compared to the 3 ft 6 in gauge of the rolling stock that is currently in active service. This move should allow access to better technology and increase line speeds.


CJ5 (DEMU) used by the Xi'an–Huyi railway

On 14 January 2014, CRRC Changchun Railway Vehicles announced that hybrid electric multiple units were put into production. At the end of 2014, the first batch of hybrid EMUs, one train each with battery-catenary power supply (EEMU) and catenary power supply-internal combustion engine (DEMU), rolled off the assembly line in Changchun. From 2016 to 2020, the vehicles were tested in Hohhot and Beijing Academy of Railway Sciences.

In September 2022, the first CJ-5 train used by the Xi'an-Huxian Railway arrived in Xi'an. The No. 0506 train, which uses an internal combustion engine and a battery hybrid, was used as a vehicle during the initial operation of the Xi'an-Huxian Railway. During the operation period, it will be temporarily managed by Xi'an Metro.

South Korea

Now retired Korail DHC-PP with new CI colour
Type of diesel Greek-German train

Korail used to operates many DMUs. The DHC (Diesel Hydraulic Car), which made its debut for the 1988 Seoul Olympics, was able to reach speeds up to 150 km/h (93 mph) and served Saemaul-ho trains. These train have retired on 2008.[citation needed]

Sri Lanka

DMUs were first introduced to Sri Lanka in 1940. The aim of this was connecting minor railway stations and stops on the main line where most express trains don't have a halt.[48]


The DMUs are now usually used on the Taiwan Railway Administration Hualien–Taitung Line, North-Link Line, South-Link Line. DMUs in Taiwan are classified as Class DR.


ASR (Sprinter) Class diesel train at Bangkok (Krungthep Station) Thailand

The State Railway of Thailand ASR class is a diesel multiple unit operated by the State Railway of Thailand. Built by British Rail Engineering Limited at Derby Litchurch Lane Works in England, it is based on the British Rail Class 158. Twenty carriages were built in 1990/91. All were painted in the same Regional Railways livery as the Class 158s.


DMU manufacturers include:

See also


  1. ^ a b "Cutting noise and smoothing the ride". Railway Gazette International. 1 August 2000. Archived from the original on 4 June 2012. Retrieved 20 January 2011. In the Voyager application, every car has a Cummins underfloor engine and alternator supplying power to a pair of body-mounted traction motors. Each drives one inner axle through a cardan shaft and axle-mounted final drive gearbox.
  2. ^ Stadler Flirt DMU/DEMU example: Elron Elektriraudtee Classes 2200, 2300 and 2400, TEXRail Stadler FLIRT
  3. ^ Holland, Julian (January 2013). An A-Z of Famous Express Trains: An Illustrated Trip Down Memory Lane. David & Charles. ISBN 9781446302958.[permanent dead link]
  4. ^ "LNER Encyclopedia: The LNER Armstrong-Whitworth Diesel–Electric Railcars". Retrieved 19 June 2016.
  5. ^ a b Heaps, Chris (1988). "End of the Blue Pullmans". BR Diary: 1968–1977. London: Ian Allan. pp. 66–67. ISBN 978-0-7110-1611-8.
  6. ^ "1976: New train speeds into service". London: BBC News. 4 October 1976. Retrieved 15 February 2011.
  7. ^ "New opportunities for the railways: the privatisation of British Rail" (PDF). Railway Archive. p. 8. Archived (PDF) from the original on 23 October 2007. Retrieved 15 February 2011.
  8. ^ a b "Class 253 High Speed Train". Railblue.co.uk. Archived from the original on 15 July 2011. Retrieved 15 February 2011.
  9. ^ a b "Class 254 High Speed Train". Railblue.co.uk. Archived from the original on 15 July 2011. Retrieved 15 February 2011.
  10. ^ "Great Western Railway calls time on long-distance HSTs". railmagazine.com. Retrieved 8 October 2022.
  11. ^ "Final batch of refurbed Inter7City trains handed over to ScotRail". RailAdvent. 13 March 2021. Retrieved 8 October 2022.
  12. ^ GWR unveils Hitachi iep trainset Archived 25 April 2018 at the Wayback Machine Railway Gazette International 30 June 2016
  13. ^ Stadler and Bombardier to supply trains for Abellio East Anglia franchise Railway Gazette International 10 August 2016
  14. ^ GWR to lease Class 769 Flex trimode trainsets Archived 27 July 2018 at the Wayback Machine Railway Gazette International 20 April 2018
  15. ^ "'They don't make trains like this anymore'". railtechnologymagazine.com. Retrieved 18 July 2019.
  16. ^ "West Midlands Trains puts first Class 230 D Train in service". Railway Technology. 23 April 2019. Retrieved 18 July 2019.
  17. ^ Hughes, Owen (10 September 2018). "New North Wales trains will be slower than Arriva ones BUT journey times will fall". northwales. Retrieved 18 July 2019.
  18. ^ Such as the Railroad Safety Appliance Act of 1893.
  19. ^ ""Kaoham Shuttle" page, Seton Lake Indian Band website (Tsalalh.net)". Archived from the original on 28 July 2014.
  20. ^ "Six Commuter Trains Purchased: Travel Easier in San Jose Costa Rica – Costa Rica Star News". 16 June 2012. Retrieved 19 June 2016.
  21. ^ Fender, Keith (5 September 2023). "Passenger equipment from Britain, US heads to Mexico". Trains. Retrieved 24 November 2023.
  22. ^ Franz, Justin; Vondrak, Otto M. "RDC Update". Railfan & Railroad (September 2020).
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  24. ^ Lewis, Bj (5 June 2012). "DCTA gets go-ahead to use Stadler cars". Denton Record-Chronicle. Archived from the original on 9 June 2012. Retrieved 6 June 2012.
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  26. ^ "TEXRail Map". Trinity Metro. Retrieved 1 April 2019.
  27. ^ "BART moves forward with $1 billion in extension projects – bart.gov". Retrieved 19 June 2016.
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  29. ^ "July 2006 Metro to Fund Implementation Study on a Regional Connector Through Glendale and Burbank". ebb.metro.net. Retrieved 1 February 2017.[permanent dead link]
  30. ^ "Coming Soon page". Retrieved 19 June 2016.
  31. ^ "BNSF Eastside Commuter Rail Feasibility Study". Archived from the original on 11 February 2010. Retrieved 21 January 2010.
  32. ^ "Alaska Railroad – Alaskan Tours & Vacations – Train Packages" (PDF). Archived from the original (PDF) on 6 March 2012. Retrieved 19 June 2016.
  33. ^ Pattison-Gordon, Jule (10 February 2016). "Fairmount line setback: No DMUs says MBTA". Bay State Banner. Retrieved 20 November 2019.
  34. ^ "Passaic Bergen Hudson Transit Project". Projects & Reports. NJ Transit. Retrieved 26 February 2021.
  35. ^ "DEMU trains begin debut run in Ctg". Bdnews24.com. Retrieved 26 May 2013.
  36. ^ "キハ43000の資料 – しるねこの微妙な生活/浮気心あれば水心!?". Archived from the original on 25 June 2016. Retrieved 19 June 2016.
  37. ^ "The Railway Museum in Saitama". Archived from the original on 13 September 2016. Retrieved 19 June 2016.
  38. ^ "New CRRC DMU on test in Malaysia". 16 May 2019.
  39. ^ Report of the General Manager for the Year Ended December 31, 1938. Reports of the General Manager (Report). Manila Railroad Company. 17 March 1939.
  40. ^ Motive Power and Rolling Stock. Report of Survey of the Manila Railroad Company and the Preliminary Survey of Railroads for Mindanao (Report). De Leuw, Cather and Company; Manila Railroad Company. July 1952. Retrieved 13 April 2021.
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  42. ^ Peadon, Brad. "April 2020". Philippine National Railways Rolling Stock Update. 3. Philippine Railways Historical Society.
  43. ^ 寺本光照 (2014). 国鉄・JR関西圏近郊電車発達史 大阪駅140年の歴史とアーバンネットワークの成立ち (in Japanese). JTBパブリッシング. p. 73. ISBN 978-4-533-09794-2. ((cite book)): |work= ignored (help)
  44. ^ "フィリピン国鉄 KIHA59「KOGANE」が営業運転に復帰" [Philippine National Railways KIHA59 "KOGANE" returns to commercial operation]. Japan Railfan Magazine Online (in Japanese). Japan: Koyusha Co., Ltd. 10 December 2019. Archived from the original on 10 December 2019. Retrieved 10 December 2019.
  45. ^ "Railway Systems-Project Record View". hyundai-rotem.co.kr. Archived from the original on 21 April 2021. Retrieved 25 December 2018.
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  48. ^ https://apps.who.int/iris/rest/bitstreams/1081775/retrieve [dead link]
  49. ^ "US Railcar". usrailcar.com.