| Multiple unit trains |
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| Subtypes |
| Technology |
| By country |
Adiesel multiple unit orDMU is amultiple-unit train powered by on-boarddiesel engines. A DMU requires no separatelocomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unitrailcars are also generally classed as DMUs. Diesel-powered units may be further classified by their transmission type: diesel–mechanicalDMMU, diesel–hydraulicDHMU, or diesel–electricDEMU.
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.
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 agearbox and driveshaft directly to the wheels of the train, like acar. The transmissions can be shifted manually by the driver, as in the great majority of first-generationBritish Rail DMUs, but in most applications, gears are changed automatically.
In a diesel–hydraulic multiple unit (DHMU), a hydraulictorque 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.
In a diesel–electric multiple unit (DEMU), adiesel engine drives anelectrical generator or analternator which produceselectrical energy. The generated current is then fed to electrictraction motors on thewheels orbogies in the same way as a conventionaldiesel–electric locomotive.[1]
On some DEMUs, such as theBombardier Voyager, each car is entirely self-contained and has its own engine, generator and electric motors.[1] In other designs, such as theBritish Rail Class 207 or theStadler GTW andStadler FLIRT DMU,[2] some cars within theconsist 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 anEMU withoutpantograph orcontact shoes (for use on the formerBritish RailSouthern Region), which "is substituted" by one or more on-boarddiesel generators; this kind of DEMU can be potentially upgraded toelectro-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]
NMBS/SNCB uses itsNMBS/SNCB Class 41 DMUs on the few remaining unelectrified lines. As electrification progresses, the DMUs become less and less important.
Diesel multiple units cover large number of passenger lines inCroatia which are operated by the national passenger service operatorHŽ 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 andSplit, are connected with an inter-city service that is provided by DMUtilting trains "RegioSwinger" (Croatian series 7123) since 2004. Those trains may also cover other lines in the country depending on need and availability.
Luxury DMU series7021, built inFrance, started to operate forYugoslav Railways in 1972 and after 1991 still remained in service of Croatian Railways until 2005. Units7121 and7122 (which came as a replacement for7221 units), together with the newest series7022 and 7023 built in 2010s Croatia, cover many of the country's local and regional services on unelectrified or partly electrified lines.
Diesel multiple units also cover large number of passenger lines in the Czech Republic which are operated by the national operatorČeské 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 theČSD used the series designations proposed byVojtěch 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 aStadler FLIRT fleet, with 20 trains DEMU version.
Germany has employed DMUs for both commuter and express services for many decades. The SVT 877Fliegender Hamburger DMU, introduced in 1933, made the run from Berlin to Hamburg in an astonishing 138 minutes, and its derivativeSVT 137 broke the land speed record in 1936. After World War 2, theVT 11.5 DMU was the flagship of the glamorousTrans 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 AdtranzClass 612 tilting train ("Regio Swinger"), theAlstom Coradia LINT (Classes 620–623, 640 and 648), theSiemens Desiro (Class 642) and theBombardier Talent (Class 643/644). From 2001 to 2016 there was even a DMU version of DB's high-speedIntercity Express, the Class 605ICE TD.
In the Republic of Ireland theCóras 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]
DMUs are used mostly on shorter or less frequently travelled routes in remote areas. The national railway companyCFR still uses, along with other DMU models,Class 77 and 78 DMUs, locally built byMalaxa between the 1930s and 50s and refurbished in the 70s. The main DMU in use is the Class 96Siemens Desiro aka Săgeata Albastră (The Blue Arrow). Private operators also largely use DMU units, mainly purchased from various French and German operators.
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In the present, several types of DMUs operate in Slovakia. Was the most common type in Slovakia is a Class 812 ZSSK based on theČD Class 810. These are used almost exclusively for hauling passenger trains on non-electrifiedregional lines and these trains often excel in low travel speeds. In the past, however, in Slovakia there were a number ofexpress trains driven bymotor 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.
The first significant use of DMUs in the United Kingdom was by theGreat Western Railway, which introduced its small but successful series of diesel–mechanicalGWR railcars in 1934. TheLondon & North Eastern Railway[4] andLondon, Midland & Scottish Railway also experimented with DMUs in the 1930s, the LMS both onits own system, and on that of itsNorthern Irish subsidiary, but development was curtailed byWorld 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 andmultiple units. The early DMUs proved successful, and under BR's1955 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 itsBlue Pullman high-speed DEMUs.[5]These were few in number and relatively short-lived,[5] but they paved the way for the very successfulInterCity 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 underClass 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 theimpact of the privatisation of British Rail in the late 1990s, several other DMU families have been introduced:[citation needed]
In 2018, the firstbi and tri-mode electro-diesel multiple units were introduced:
Canada generally follows similar buffer strength requirements to the US,[19] but new services are evaluated on a case-by-case basis. As a result, several types of lightweight DMUs have been used:
Costa Rica has purchased several Apolo 2400 series DMU railcars from the former narrow gauge operator in Spain, which are run in commuter service.[21]
42X'Trapolis Tsíimin K'áak train sets have been ordered forTren Maya, 10 of which are DMU and 32 are EDMU.[22]
A type of diesel multiple units in the U.S. was theBudd Rail Diesel Car (RDC). The RDC was a single passenger car with two diesel engines and two sets of controls.[23]
In the United States, DMU systems must be FRA-compliant to be permitted on freight rail corridors. TheFederal Railway Administration has mandated highercoupling strength requirements than European regulators, effectively prohibiting the use of lighter weight European-styleinter-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.[24]
Operations using FRA-compliant vehicles:
Operations using non FRA-compliant vehicles:
Proposed operations:
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 theSavannahlander andGulflander 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–Faujdarhat line. These DEMUs also operate on theChittagong Circular Railway and on theBangladesh Railway's service betweenDhaka andNarayanganj.[36] However, these trains faced reliability issues soon after the final delivery in 2015, with all 20 trains becoming inoperable past 2018.[37] In 2020, technicians from Bangladesh Railway were able to repair one of the inoperative trains to working condition. However, the proposed project to repair the rest of the trains were deemed to be too expensive in the long run.[38] By January 2025, after 10 years of service, Bangladesh Railway announced its intention to sell the DEMU trains as scrap.[37]
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
TheDongfeng DMU was first Chinese diesel multiple unit produced byQingdao Sifang in 1958.
TheChina Railway NZJ was China's first double-decker diesel multiple unit is an ideal medium- and short-distance rail transport vehicle. It was independently developed and manufactured byTangshan Works in 1998 and put into operation betweenNanchang andJiujiang in June of that year.[39]
TheChina Railway NYJ1 [zh] was China's first hydraulic transmission diesel multiple unit class was developed byQingdao Sifang at the end of 1998 and put into operation betweenNanchang andJiujiang andNanchang andGanzhou in February 1999.[39]
TheChina Railway NZJ1 [zh] "New Dawn" was higher-speeddouble-decker diesel multiple unit was jointly developed byQishuyan Works andNanjing Puzhen Works in August 1999, and put into commercial operation on theShanghai-Nanjing Railway in October of that year.[39]
TheChina Railway NDJ3 "Great Wall", previously labeled the "Harmony Great Wall" is the onlyhigher-speed diesel multiple unit that is still operating in China. It was first designed to be used for passenger transport in the 2008 Olympics, and has become a mature technology platform with export orders to Nigeria despite initial flaws related to overheating of electrical cables in the power car.
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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 theXi'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 byXi'an Metro.
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DMUs (particularly 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 aWDM-2 orWDM-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 anMEMU train service in 2018.
India's first and largest DMU shed atJalandhar, Punjab, holds more than 90 units placed in service all over Punjab.The DMU services in India have had various different classes. They can be classified as
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State-owned companyPT.INKA builds several type of DMU, some of which operate in urban and suburban areas.
In Japan, where gasoline-driven railbuses (on small private lines) and railmotors (Kihani 5000 of thenational railways) had been built since the 1920s, the first two streamlined DMUs came in service in 1937, classKiha 43000 (キハ43000系).[40]
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 duringWorld War II.[41]
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.
TheKeretapi Tanah Melayu (KTM) has a total of 13 DMUKTM Class 61 ordered fromCRRC 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.[42]
ThePhilippine 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 tostreamliner units by 1932 for first-class services on the South Main Line between Manila andLegazpi, Albay.[43] Since then, generations of DMUs were used chiefly for short-distance commuter services by the PNR in the island ofLuzon.[44][45]
Even without activeinter-city rail services in the present-day, DMUs are still used on thePNR Metro Commuter Line inMetro Manila and the Bicol Commuter service in theBicol Region.[46] Three generations of DMUs are in use: second-hand DMUs handed over byJR East such as theKiHa 35,52 and59 series originally built in the 1960s and acquired in the early 2010s,[47][48] theRotem DMUs of 2009 built byKorean manufacturerHyundai Rotem,[49] and the8000 and8100 classes built byIndonesian firmPT INKA.[50][51]
From 2022 onwards, the PNR will purchasestandard gauge DMUs for its upcoming inter-city rail network in Luzon andMindanao. This is compared to the3 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.
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 servedSaemaul-ho trains. These train have retired on 2008.[citation needed]
DMUs were first introduced toSri 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.[52]
The DMUs are now usually used on theTaiwan Railway AdministrationHualien–Taitung Line,North-Link Line,South-Link Line. DMUs in Taiwan are classified as Class DR.
Thailand
The State Railway of ThailandASR class is a diesel multiple unit operated by theState Railway of Thailand. Built byBritish Rail Engineering Limited atDerby Litchurch Lane Works in England, it is based on theBritish Rail Class 158. Twenty carriages were built in 1990/91. All were painted in the sameRegional Railways livery as the Class 158s.
DMU manufacturers include:
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.
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