Multiple unit
Overview
 
The term multiple unit or MU is used to describe a self-propelled carriages capable of coupling with other units of the same or similar type and still being controlled from one driving cab. The term is commonly used to denote passenger trainsets consisting of more than one carriage. Single self-propelling carriages (also called railcar
Railcar
A railcar, in British English and Australian English, is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach , with a driver's cab at one or both ends. Some railways, e.g., the Great Western...

s, rail motor coach
Rail motor coach
A motor coach or motorcar is a powered rail vehicle able to pull several trailers and at the same time transport passengers or luggage. With multiple unit train control, one operator can control several “motor coaches” efficiently in the same train, making longer trains possible, it can be part of...

es or railbus
Railbus
A railbus is a very lightweight type passenger rail vehicle that shares many aspects of their construction with a bus, usually having a bus, or modified bus body, and having four wheels on a fixed base, instead of on bogies...

es) can be referred to as multiple units if capable of operating with other units.

Multiple units are classified by their power source and are of two main types: electric multiple unit
Electric multiple unit
An electric multiple unit or EMU is a multiple unit train consisting of self-propelled carriages, using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a number of the carriages...

 (EMU) or diesel multiple unit
Diesel multiple unit
A diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:...

 (DMU).
Encyclopedia
The term multiple unit or MU is used to describe a self-propelled carriages capable of coupling with other units of the same or similar type and still being controlled from one driving cab. The term is commonly used to denote passenger trainsets consisting of more than one carriage. Single self-propelling carriages (also called railcar
Railcar
A railcar, in British English and Australian English, is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach , with a driver's cab at one or both ends. Some railways, e.g., the Great Western...

s, rail motor coach
Rail motor coach
A motor coach or motorcar is a powered rail vehicle able to pull several trailers and at the same time transport passengers or luggage. With multiple unit train control, one operator can control several “motor coaches” efficiently in the same train, making longer trains possible, it can be part of...

es or railbus
Railbus
A railbus is a very lightweight type passenger rail vehicle that shares many aspects of their construction with a bus, usually having a bus, or modified bus body, and having four wheels on a fixed base, instead of on bogies...

es) can be referred to as multiple units if capable of operating with other units.

Multiple units are classified by their power source and are of two main types: electric multiple unit
Electric multiple unit
An electric multiple unit or EMU is a multiple unit train consisting of self-propelled carriages, using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a number of the carriages...

 (EMU) or diesel multiple unit
Diesel multiple unit
A diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:...

 (DMU). Diesel-powered units may be further classified by their transmission type: diesel-electric (DEMU), diesel-mechanical (DMMU) or diesel-hydraulic (DHMU).

Locomotives utilising multiple-unit train control
Multiple-unit train control
Multiple-unit train control, sometimes abbreviated to multiple-unit or MU, is a method of simultaneously controlling all the traction equipment in a train from a single location, whether it is a Multiple unit comprising a number of self-powered passenger cars or a set of locomotives.A set of...

 are not multiple units.

History

Multiple-unit train control was first used in Electric Multiple Units in the 1890s.
This allowed electrically
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

-powered rapid transit
Rapid transit
A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...

 trains to be operated from a single driving position.
Early users of such multiple units include the Liverpool Overhead Railway
Liverpool Overhead Railway
The Liverpool Overhead Railway was the world's first electrically operated overhead railway. The railway was carried mainly on iron viaducts, with a corrugated iron decking, onto which the tracks were laid. It ran close to the River Mersey in Liverpool, England, following the line of Liverpool Docks...

 (the first multiple units) and Chicago's South Side Elevated Railroad
South Side Elevated Railroad
The South Side Elevated Railroad was the first elevated rapid transit line in Chicago, Illinois. The line ran from downtown Chicago to Jackson Park, with branches to Englewood, Normal Park, Kenwood, and the Union Stock Yards...

 (the first units to use a low-voltage control system).

Steam-powered ancestors

The United Kingdom and France (for example Voiture État à 2 étages
Voiture État à 2 étages
The Voiture État à deux étages, or approximately translated État double-deck passenger car, were a class of double-deck carriages built for the Chemin de Fer de l'État of France.-Origin:...

) had many examples of push-pull
Push-pull train
Push–pull is a mode of operation for locomotive-hauled trains allowing them to be driven from either end.A push–pull train has a locomotive at one end of the train, connected via some form of remote control, such as multiple-unit train control, to a vehicle equipped with a control cab at the other...

 steam trains, or autotrain
Autotrain
Autotrain may refer to:* Autotrain, a type of push-pull train incorporating a steam locomotive and specially fitted passenger coaches* Auto Train, a specific Amtrak passenger service* Auto-Train Corporation...

s and railmotor
Railmotor
Railmotor is a term which was used by several British railway companies for a steam railcar.-Overview:William Bridges Adams started building railmotors as early as 1848, but only in small numbers...

s on branch lines which include at least partial control of a steam locomotive from a remote cab. These provided many of the operational benefits of a multiple unit, although none incorporated any form of electrical/electronic multiple-unit train control
Multiple-unit train control
Multiple-unit train control, sometimes abbreviated to multiple-unit or MU, is a method of simultaneously controlling all the traction equipment in a train from a single location, whether it is a Multiple unit comprising a number of self-powered passenger cars or a set of locomotives.A set of...

.

Design

Most MUs are powered either by traction motors, receiving their power through a live rail or overhead wire
Overhead lines
Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...

 (EMU
Electric multiple unit
An electric multiple unit or EMU is a multiple unit train consisting of self-propelled carriages, using electricity as the motive power. An EMU requires no separate locomotive, as electric traction motors are incorporated within one or a number of the carriages...

), or by a diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

 driving the wheels through a gearbox or hydraulic transmission (DMU
Diesel multiple unit
A diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:...

). Diesel-electric multiple units
Demu
Demu may refer to:*Dému, a village in France*Diesel-electric Multiple Unit *DEMU, Diesel and Electric Modellers United, a UK railway modelling group*The alien antagonists of The Demu Trilogy by F.M. Busby...

 (DEMUs) have a diesel engine that drives a generator producing electricity to drive traction motors in a similar fashion to a diesel-electric locomotive.

A multiple-unit trainset has the same power and traction components as a locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...

, but instead of the components being concentrated in one carbody, they are spread out on each car that makes up the set. In many cases these cars can only propel themselves when they are part of the set, so they are semi-permanently coupled. For example, a DMU might have one car carry the prime mover
Prime mover (locomotive)
In engineering, a prime mover is an engine that converts fuel to useful work. In locomotives, the prime mover is thus the source of power for its propulsion. The term is generally used when discussing any locomotive powered by an internal combustion engine...

 and traction motor
Traction motor
Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion ....

s, and another the engine for head end power
Head end power
Head end power or electric train supply is a rail transport term for the electrical power distribution system on a passenger train. The power source, usually a locomotive at the front or “head” of a train or a generator car, generates all the electricity used for lighting, electrical and other...

 generation; an EMU might have one car carry the pantograph
Pantograph (rail)
A pantograph for rail lines is a hinged electric-rod device that collects electric current from overhead lines for electric trains or trams. The pantograph typically connects to a one-wire line, with the track acting as the ground wire...

 and transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...

, and another car carry the traction motors.

It is not necessary for every single car in an MU set to be motorized. Therefore MU cars can be motor units or trailer units. Instead of motors, trailing units can contain supplementary equipment such as air compressors, batteries, etc.; trailer cars may also be fitted with a driving cab.

In most cases, MU trains can only be driven/controlled from dedicated cab cars. However, in some MU trains, every car is equipped with a driving console, and other controls necessary to operate the train, therefore every car can be used as a cab car whether it is motorised or not, if on the end of the train. An example of this arrangement is the NJ Transit Arrows.

Examples

Virtually all rapid transit
Rapid transit
A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...

 rolling stock, such as ones used on the New York City Subway
New York City Subway
The New York City Subway is a rapid transit system owned by the City of New York and leased to the New York City Transit Authority, a subsidiary agency of the Metropolitan Transportation Authority and also known as MTA New York City Transit...

, the London Underground
London Underground
The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...

, and other subway systems, are multiple-unit trainsets, usually EMUs. Most trains in the Netherlands and Japan are MUs, making them suitable for use in areas of high population density.

Many high-speed rail
High-speed rail
High-speed rail is a type of passenger rail transport that operates significantly faster than the normal speed of rail traffic. Specific definitions by the European Union include for upgraded track and or faster for new track, whilst in the United States, the U.S...

 rolling stocks are also multiple-unit trainsets, such as the Japanese Shinkansen
Shinkansen
The , also known as THE BULLET TRAIN, is a network of high-speed railway lines in Japan operated by four Japan Railways Group companies. Starting with the Tōkaidō Shinkansen in 1964, the network has expanded to currently consist of of lines with maximum speeds of , of Mini-shinkansen with a...

and the latest-generation German InterCityExpress
InterCityExpress
The Intercity-Express or ICE is a system of high-speed trains predominantly running in Germany and neighbouring countries. It is the highest service category offered by DB Fernverkehr and is the flagship of Deutsche Bahn...

 ICE 3
Siemens Velaro
Siemens Velaro is a family of high-speed EMU trains used in Europe and China. The Velaro is based on Deutsche Bahn's ICE 3 high-speed trains, but is a full Siemens product unlike the ICE 3 which involved other manufacturers....

 high-speed trains
High-speed rail
High-speed rail is a type of passenger rail transport that operates significantly faster than the normal speed of rail traffic. Specific definitions by the European Union include for upgraded track and or faster for new track, whilst in the United States, the U.S...

. A new high-speed MU, the AGV
Automotrice à grande vitesse
The Automotrice à grande vitesse ' is an Alstom train intended as the successor to France’s TGV high-speed trains; the name stands for automotrice à grande vitesse, or ‘high-speed self-propelled carriage’...

, was unveiled by France's Alstom
Alstom
Alstom is a large multinational conglomerate which holds interests in the power generation and transport markets. According to the company website, in the years 2010-2011 Alstom had annual sales of over €20.9 billion, and employed more than 85,000 people in 70 countries. Alstom's headquarters are...

 on February 5, 2008. It has a claimed service speed of 360 km/h.

Freight multiple units

A new concept is to use the multiple unit idea for freight traffic, such as carrying containers or for trains used for maintenance. The Japanese M250 series
M250 series
The M250 Series Super Rail Cargo is a freight electric multiple unit operated by JR Freight in Japan. It entered service in 2004 with the objective of reducing emissions and carrying general freight for small package forwarders . The M250 series is JR Freight's first container train with...

 train has four front and end carriages that are EMUs, and has been operating since March 2004. The German CargoSprinter
CargoSprinter
The CargoSprinter is a multiple unit freight car;it could also be thought of as a container truck that runs on rails.Built by the German company Windhoff, it is in effect a self-propelled flatcar for containers...

 have been used in three countries since 2003.

Advantages

Multiple units have several advantages over locomotive-hauled trains:
  • Energy efficiency — MUs are more energy-efficient than locomotive-hauled trains. They are more nimble, especially on gradients, as much more of the train's weight (sometimes all of it) is carried on power-driven wheels, rather than the train having to haul the dead weight of unpowered hauled coaches. In addition, they have a lower weight-per-seat value than a locomotive-hauled train since they do not have a bulky locomotive that does not itself carry passengers, but contributes to the total weight of the train. This is particularly important where train services make frequent stops, since the energy consumed for accelerating the train increases significantly with an increase in weight.

  • Higher acceleration rate — Because of the energy efficiency, higher power-to-weight ratio and higher adhesive-weight-to-total-weight ratio values, MUs generally have higher acceleration ability than locomotive-type trains and are favored in urban trains and subway (metro) systems for frequent start/stop routines.

  • No need to turn locomotive — Most MUs have cabs at both ends, resulting in quicker turnaround times, reduced crewing costs, and enhanced safety. The faster turnaround time and the reduced size (due to higher frequencies) as compared to large locomotive
    Locomotive
    A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...

    -hauled trains, has made the MU a major part of suburban commuter rail services in many countries. MUs are also used by most rapid transit
    Rapid transit
    A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...

     systems. However, this is no longer a problem for locomotive-hauled trains due to the increasing use of push-pull train
    Push-pull train
    Push–pull is a mode of operation for locomotive-hauled trains allowing them to be driven from either end.A push–pull train has a locomotive at one end of the train, connected via some form of remote control, such as multiple-unit train control, to a vehicle equipped with a control cab at the other...

    s.

  • Makeup can be changed mid-journey — MUs may usually be quickly made up or separated into sets of varying lengths. Several multiple units may run as a single train, then be broken at a junction point into shorter trains for different destinations.

  • Reliability — As there are multiple engines, or motors, the failure of one engine does not prevent the train from continuing its journey. A locomotive-drawn train typically has only one power unit, whose failure will disable the train. However, some locomotive-hauled trains may contain more than one power unit and thus be able to continue at reduced speed after the failure of one.


  • Axle load — Multiple units have lighter axle loads, allowing operation on lighter tracks, where locomotives may be banned. Another side-effect of this is reduced track wear, as traction forces can be provided through many axles, rather than just the four or six of a locomotive.

  • Easy and quick driving — Multiple units generally have rigid couplers instead of the flexible ones often used on locomotive-hauled trains. That means that brakes or throttle can be more quickly applied without an excessive amount of jerk experienced in passenger coaches.

  • Allowance for accurate performance calculations for timetabling purposes — In a locomotive-hauled train, if the number of cars is changed in order to meet the demand, acceleration and braking performance will also change. This calls for performance calculations to be done taking the heaviest train composition into account. This may sometimes cause some trains in off-peak periods to be overpowered with respect to the required performance. When two or more multiple units are coupled, train performance remains almost unchanged. However, in locomotive-hauled train compositions, using more powerful locomotives when a train is longer can solve this problem.

Disadvantages

Multiple units do have some disadvantages as compared to locomotive-hauled trains:
  • Maintenance - It may be easier to maintain one locomotive than many self-propelled cars.

  • Safety - In the past it was often safer to locate the train's power systems away from passengers. This was particularly the case for steam locomotives, but still has some relevance for other power sources. A head-on collision or level-crossing accident involving a multiple unit (with passengers potentially right at the front of the train) is likely to result in more casualties than one with a locomotive (where the heavy locomotive would act as a 'crumple zone').

  • Easy replacement of motive power - If a locomotive fails, it can be easily replaced with minimal shunting movements. There would be no need for passengers to evacuate the train. Failure of a multiple unit will often require a whole new train and time-consuming switching activities; also passengers would be asked to evacuate the failed train and board another one.

  • Efficiency - Idle trains do not waste expensive motive power resources. Separate locomotives mean that the costly motive power assets can be moved around as needed and also used for hauling freight trains. A multiple-unit arrangement would limit these costly motive power resources to use in passenger transportation.

  • Gangways - It is difficult to have gangways between coupled sets, and still retain an aerodynamic leading front end. Because of this fact, frequently there is no passage between high-speed coupled sets. In such instances more crew may be required, so that ticket inspectors, for example, can be present in all of them. This leads to higher crew costs and lower utilization of crew resources. In a locomotive-hauled train, one single crew can serve all the train regardless of the number of cars in the train provided limits of individual workload are not exceeded. Likewise, in such instances, buffet cars and other shared passenger facilities may need to be duplicated in each train set, reducing efficiency.

  • Flexibility - Large locomotives can be substituted for small locomotives when more power is needed. Also, different types of passenger cars (such as reclining-seats, compartment cars, couchettes, sleepers, restaurant cars, buffet cars, etc.) can be easily added to or removed from a locomotive-hauled train. This is not so easy for a multiple unit, since individual cars can be attached or detached only in a maintenance facility. This also allows a loco-hauled train to be flexible in terms of number of cars. Cars can be removed or added one by one, but in multiple units two or more units have to be coupled. This is not so flexible.

  • Noise and vibration - The passenger environment of a multiple unit is often noticeably noisier than that of a locomotive-hauled train, due to the presence of underfloor machinery. The same applies to vibration. This is a particular problem with DMU
    Diesel multiple unit
    A diesel multiple unit or DMU is a multiple unit train consisting of multiple carriages powered by one or more on-board diesel engines. They may also be referred to as a railcar or railmotor, depending on country.-Design:...

    s.

  • Obsolescence cycles - Separating the motive power from the payload-carrying cars means that either can be replaced when obsolete without affecting the other.

Australia

In 1964, Tulloch Limited
Tulloch Limited
Tulloch Limited was a major Australian engineering and railway rolling stock manufacturer, located at Rhodes, New South Wales. It was founded by Robert Tulloch and began in 1913 as Tulloch's Phoenix Iron Works, which had been working at the Phoneix Iron Works, Pyrmont. During the Second World War,...

 built the first double-decker trailer cars for use in Sydney
Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...

; they ran with single deck electric motor cars. The first prototype double deck motor car was built by Comeng
Commonwealth Engineering
The Commonwealth Engineering Company Limited is the brand name of a former Australian Engineering Company that designed Locomotives, Electrical Multiple Units , Diesel Multiple Units and Trams.-History:...

 in 1969 and production versions entered service in 1972; these were the first fully double deck EMU passenger trains in the world. All CityRail
CityRail
CityRail is an operating brand of RailCorp, a corporation owned by the state government of New South Wales, Australia. It is responsible for providing commuter rail services, and some coach services, in and around Sydney, Newcastle and Wollongong, the three largest cities of New South Wales. It is...

 electric commuter trains in Sydney
Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...

 are now double deck. They all have two doors per side per carriage, with a vestibule at each end at platform height. Well-known examples of these trains are the Tangara and Millennium train
Millennium train
The CityRail Millennium or M set is a class of electric multiple unit operated by CityRail in Sydney, New South Wales, Australia.It is one of CityRail's newest members of the fleet and was the first "4th generation train" on the network. The fourth generation trains were put into service from July...

s. The Sydney double deck commuter trains are 14 foot high.

The Public Transport Corporation
Public Transport Corporation
The Public Transport Corporation was a State Government of Victoria owned corporate body formed under the Transport Act 1983 which operated passenger and freight trains, trams and bus services in Victoria, Australia....

 in Melbourne
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...

 ordered a prototype Double Deck Development and Demonstration
4D (train)
The 4D was a prototype double deck electric multiple unit train built for the Public Transport Corporation of Melbourne, the state capital of Victoria, Australia. It remains the only double deck train ever to have run in Melbourne.-Design:Built by A Goninan & Co...

 train in 1991. It suffered frequent breakdowns and spent long periods out of use. It was finally withdrawn in 2002 and scrapped in 2006.

Ireland

CIE
Córas Iompair Éireann
Córas Iompair Éireann , or CIÉ, is a statutory corporation of the Irish state, answerable to the Irish Government and responsible for most public transport in the Republic of Ireland and, jointly with its Northern Ireland counterpart, the Northern Ireland Transport Holding Company, between the...

 introduced its first DMUs
GNRI AEC Class
After 1945, both CIE and the GNR found themselves in a poor financial position as a result of the deprivations of World War II and increased competition from road traffic. They looked to diesel power as a way to streamline costs and bring them back into profitability...

, the 2600-class, in 1951.

People's Republic of China

The concept of multiple unit has entered the horizon of the Chinese since the 6th Speed-up Campaign of China Railways
China Railways
China Railways is the national railway operator of the People's Republic of China, under the Chinese Ministry of Railways.China Railways operates rail commuter and freight transport via several smaller companies....

 in 2007.With the upgrade of Jinghu Railway
Jinghu railway
The Beijing–Shanghai Railway or Jinghu railway is a railway line in China between Beijing and Shanghai. The line has a total length of 1,462 kilometres and connects the municipalities of Beijing, Tianjin, and Shanghai, as well as the provinces of Hebei, Shandong, Anhui and Jiangsu...

,North Jingguang Railway
Jingguang Railway
The Beijing–Guangzhou Railway or Jingguang Railway is a major arterial railway in the China that connects Beijing in the north with Guangzhou in the south. This dual-track electrified line has a total length of 2,324 kilometres and spans five provinces through north, central and south China...

, Jingha Railway and Hukun Railway,and the construction of new Passenger Dedicated Lines(or Passenger Railways) completed, CRH
China Railway High-speed
China Railway High-speed ; ) is the high-speed rail system operated by China Railways.Hexie Hao is the designation for high-speed trains running on this rail system. At the middle of the run, all trains were marked "CRH" on the centre of the head vehicle and the side of the walls of each vehicle...

(China Railway High-speed) trains have been put into service, mainly in North and Northeast China, and East China. All these CRH trains are electric multiple units. This could be seen as the beginning of the general service of multiple unit trains in China's national railway system.

Far earlier than the birth of CRH brand, multiple unit trains have been running on all major cities' metro lines in China.

Japan

In Japan, most passenger train vehicles including the high-speed Shinkansen
Shinkansen
The , also known as THE BULLET TRAIN, is a network of high-speed railway lines in Japan operated by four Japan Railways Group companies. Starting with the Tōkaidō Shinkansen in 1964, the network has expanded to currently consist of of lines with maximum speeds of , of Mini-shinkansen with a...

 are multiple unit type. The few locomotive passenger trains still in use are mostly used for overnight sleeper trains and tourist-oriented trains such as the numerous steam locomotives operated infrequently on several of the more scenic lines throughout the country.

Japan is a country of high population density with a large number of railway passengers in relatively small urban areas, and frequent operation of short-distance trains has been required. Therefore, the high acceleration ability and quick turnaround times of MU have advantages, encouraging their development in this country. Additionally, the mountainous terrain gives the MU's advantage on grade more importance than in most countries, particularly in driving adoption on small private lines many of which run from coastal cities to small towns in the mountains.

Most long-distance trains in Japan had been operated by locomotives until the 1950s, but by utilizing and enhancing the technology of short-distance urban MU trains, long-distance express MU-type vehicles were developed and widely introduced starting in the mid-1950s. This work resulted in the original Bullet Train
Bullet train
Bullet train may refer to:* The Shinkansen high speed trains of Japan, so nicknamed for their appearance and speed* Other high speed trains of a similar appearance to the original Japanese trains...

 development which optimized all of the EMU's efficiencies to maximize speed. It was introduced upon completion of the Tokaido Shinkansen (literally "new line") in 1964. By the 1970s, locomotive type trains were regarded as slow and inefficient, and their use is now mostly limited to freight. Recently there have been development efforts in freight EMU
M250 series
The M250 Series Super Rail Cargo is a freight electric multiple unit operated by JR Freight in Japan. It entered service in 2004 with the objective of reducing emissions and carrying general freight for small package forwarders . The M250 series is JR Freight's first container train with...

 technology, but it is currently only utilized for an express freight service on the Tokaido Main Line
Tokaido Main Line
The is the busiest trunk line of the Japan Railways Group , connecting Tōkyō and Kōbe stations. It is long, not counting its many freight feeder lines around the major cities...

 between Tokyo and Osaka; the government has been pushing for the adoption of freight EMU technology on energy efficiency grounds in the hopes that wide adoption could assist in meeting emissions targets. The effort has been principally targeted at express package shipping that would otherwise travel by road.

Russia

Elektrichka is an informal word for elektropoezd , a Soviet
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 or post-Soviet regional (mostly suburban) electrical multiple unit passenger train
Train
A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...

. Elektrichkas are widespread in Russia, Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...

 and some other countries of the former Soviet Union. The first elektrichka ride occurred in August 1929 between Moscow and Mytishchi
Mytishchi
Mytishchi is a city and the administrative center of Mytishchinsky District of Moscow Oblast, Russia, which lies to the northeast of Russia's capital Moscow, on the Yauza River and the Moscow–Yaroslavl railroad. The city is the oblast's largest center for industry and education...

.

United Kingdom

In Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...

 the majority of passenger services have been operated by diesel multiple units since the mid-1950s under the tenure of both the Ulster Transport Authority
Ulster Transport Authority
The Ulster Transport Authority ran rail and bus transport in Northern Ireland from 1948 until 1966.-Formation and consolidation:The UTA was formed by the Transport Act 1948, which merged the Northern Ireland Road Transport Board and the Belfast and County Down Railway...

 (1948–1966) and Northern Ireland Railways
Northern Ireland Railways
NI Railways, also known as Northern Ireland Railways and for a brief period of time, Ulster Transport Railways , is the railway operator in Northern Ireland...

 (since 1967). In the UK the use of modern diesel multiple units was pioneered in Northern Ireland, although a number of other railway companies also experimented with early DMUs (including the Great Western and the London Midland Scottish). Notable examples include the Sprinter
Sprinter (train)
The Sprinter is a family of diesel multiple unit trains in use on the UK railway system. They were built in the 1980s and early 1990s by BREL, Metro Cammell and Leyland. Most are based around a Cummins engine with Voith hydraulic transmission, although some class 158s have a Perkins engine...

 and Voyager
Bombardier Voyager family
The Voyager series is a group of express diesel-electric multiple-unit trains built by Bombardier Transportation for service on the UK railway network.-Class 220:...

 families, and the brand new Olympic Javelin
British Rail Class 395
British Rail Class 395 is a dual-voltage electric multiple unit used by train operating company Southeastern for its services along High Speed 1 and onwards to the Kent coast. The trains were built in Japan by Hitachi and shipped to the United Kingdom to operate new high speed domestic services...

 train service.

The London Underground passenger system is operated exclusively by EMUs. Work trains on the Underground employ separate locomotives, some of which are dual battery/live rail powered.

United States and Canada

Most long-distance trains in North America are locomotive-hauled and use a process called Multi-Unit control to control multiple locomotives, this does not make these locomotives MUs. However, commuters, rapid transit
Rapid transit
A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...

, and light rail
Light rail
Light rail or light rail transit is a form of urban rail public transportation that generally has a lower capacity and lower speed than heavy rail and metro systems, but higher capacity and higher speed than traditional street-running tram systems...

 operations make extensive use of MUs. Most electrically powered trains are MUs. The Southeastern Pennsylvania Transportation Authority (SEPTA) Regional Rail Division uses EMUs almost exclusively — the exception being some of its peak express service. New Jersey Transit
New Jersey Transit
The New Jersey Transit Corporation is a statewide public transportation system serving the United States state of New Jersey, and New York, Orange, and Rockland counties in New York State...

 service on the Northeast Corridor Line
Northeast Corridor Line
The Northeast Corridor Line is a commuter rail operation run by New Jersey Transit along Amtrak's Northeast Corridor. It is the successor to commuter services provided by the Pennsylvania Railroad along the section between Trenton, New Jersey and New York Penn Station...

 is split between electric locomotives and EMUs.

M2
M2 (railcar)
The M2 is a series of 244 electric multiple unit cars produced for the Metropolitan Transportation Authority and the Connecticut Department of Transportation for use on the New Haven Line...

, M4, M6 and M8
M8 (railcar)
The M8 is an electric multiple unit railroad car built by Kawasaki for use on the New Haven Line of the Metro-North Railroad. It will replace the current fleet of 240 M2's which are nearing 40 years old and the 54 M4's which entered service in 1987.-Design:...

 EMUs which operate on the New Haven Line of Metro-North Railroad
Metro-North Railroad
The Metro-North Commuter Railroad , trading as MTA Metro-North Railroad, or, more commonly, Metro-North, is a suburban commuter rail service that is run and managed by the Metropolitan Transportation Authority , an authority of New York State. It is the busiest commuter railroad in the United...

, are “multi-system
Multi-system (rail)
A Multi-system locomotive is one that is able to operate using more than one railway electrification system, such as the British Rail Class 92 which can operate from both 750 V DC third rail and 25 kV, 50 Hz AC from overhead lines.As well as multi-system electric...

” meaning they can draw power from either the third rail or from overhead lines
Overhead lines
Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point...

. This allows operation under the wires between Pelham, NY
Pelham (Metro-North station)
The Pelham Metro-North Railroad station serves passengers who wish to travel to or from Pelham, New York, via the New Haven Line. The station is one mile west of the point where the New Haven Line joins the Northeast Corridor and just east of the end of third rail power and start of overhead...

 and New Haven, CT
Union Station (New Haven)
Union Station, also known as New Haven Railroad Station, is the main railroad passenger station in New Haven, Connecticut. Designed by noted American architect Cass Gilbert, the beaux-arts Union Station was completed and opened in 1920 after the previous Union Station was...

, a section of track owned by Metro North but shared with Amtrak's Northeast Corridor service, and on third rail between Pelham and Grand Central Terminal
Grand Central Terminal
Grand Central Terminal —often incorrectly called Grand Central Station, or shortened to simply Grand Central—is a terminal station at 42nd Street and Park Avenue in Midtown Manhattan in New York City, United States...

. EMUs are used on AMT
Agence métropolitaine de transport
The Agence métropolitaine de transport is the umbrella organization that plans, integrates, and coordinates public transportation services across Canada's Greater Montreal Region, including the Island of Montreal, Laval , and communities along both the North Shore of the Rivière des Mille-Îles...

's Montreal/Deux-Montagnes line.

DMUs are less common, partly because new light rail operations are almost entirely electric, with many commuter routes already electrified, and also because of the difficulties posed by Federal Railway Administration rules limiting their use on shared passenger/freight corridors. When the Budd RDC was developed following World War II, it was adopted for many secondary passenger routes in the United States (especially on the Boston and Maine Railroad
Boston and Maine Railroad
The Boston and Maine Corporation , known as the Boston and Maine Railroad until 1964, was the dominant railroad of the northern New England region of the United States for a century...

) and Canada. These operations generally survived longer in Canada, but several were abandoned in the Via Rail
VIA Rail
Via Rail Canada is an independent crown corporation offering intercity passenger rail services in Canada. It is headquartered near Montreal Central Station at 3 Place Ville-Marie in Montreal, Quebec....

 cutbacks of the early 1990s. One that survives is Victoria – Courtenay train on Vancouver Island.

DMUs are used on the RiverLINE
River Line (New Jersey Transit)
The River Line is a diesel light rail system in New Jersey, United States, that connects the cities of Camden and Trenton, New Jersey's capital. It is operated for New Jersey Transit by the Southern New Jersey Rail Group , which originally included Bechtel Group and Bombardier...

 in New Jersey. Currently Colorado Railcar
Colorado Railcar
Colorado Railcar was a manufacturer of railroad rolling stock, railcars and diesel multiple unit commuter vehicles. Both products come in single- and double-level versions. It shut down in 2008, with its assets being purchased by US Railcar.-History:...

 is demonstrating an FRA Crash Compliant DMU in the United States. NJ Transit has experimented with this DMU on the Princeton Branch
Princeton Branch
The Princeton Branch is a commuter rail line and service owned and operated by New Jersey Transit in the U.S. state of New Jersey. The line is a short branch of the Northeast Corridor Line, running from Princeton Junction northwest to Princeton with no intermediate stops...

 line. In August 2006 it was announced that Amtrak wants the State of Vermont to experiment with DMUs on the state-subsidized Vermonter line from New Haven north to St. Albans
St. Albans (city), Vermont
St. Albans is a city in and the shire town of Franklin County, Vermont, in the United States. At the 2000 census, the city population was 7,650. St Albans City is completely surrounded by St. Albans town, which is incorporated separately from the city of St. Albans...

 to replace the less efficient diesel locomotive trainsets currently used.

MU streetcars were used in Toronto by the Toronto Transportation Commission
Toronto Transportation Commission
Before 1954, the Toronto Transit Commission was called the Toronto Transportation Commission.-History:Toronto's first public transportation company was the Williams Omnibus Bus Line and owned by undertaker Burt Williams. The franchise carried passengers in horse-drawn stagecoaches along Yonge...

 (later Toronto Transit Commission
Toronto Transit Commission
-Island Ferry:The ferry service to the Toronto Islands was operated by the TTC from 1927 until 1962, when it was transferred to the Metro Parks and Culture department. Since 1998, the ferry service is run by Toronto Parks and Recreation.-Gray Coach:...

) from 1949 to 1966 using 100 PCC A-7 built by St. Louis Car Company
St. Louis Car Company
The St. Louis Car Company was a major United States manufacturer of railroad passenger cars, streetcars, trolleybuses and locomotives that existed from 1887–1973, based in St. Louis, Missouri.-History:...

 and Canadian Car and Foundry
Canadian Car and Foundry
Canadian Car and Foundry also variously known as "Canadian Car & Foundry," or more familiarly as "Can Car," manufactured buses, railroad rolling stock and later aircraft for the Canadian market...

. These two car units ran along the Bloor Street route only and ceased operations after the opening of the Bloor–Danforth subway line. The A-7 units were later converted to single use.

See also

  • Rail terminology
    Rail terminology
    Rail terminology is a form of technical terminology. The difference between the American term railroad and the international term railway is the most obvious difference in rail terminology...

  • Rail motor coach
    Rail motor coach
    A motor coach or motorcar is a powered rail vehicle able to pull several trailers and at the same time transport passengers or luggage. With multiple unit train control, one operator can control several “motor coaches” efficiently in the same train, making longer trains possible, it can be part of...

  • Railbus
    Railbus
    A railbus is a very lightweight type passenger rail vehicle that shares many aspects of their construction with a bus, usually having a bus, or modified bus body, and having four wheels on a fixed base, instead of on bogies...

     / Railcar
    Railcar
    A railcar, in British English and Australian English, is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach , with a driver's cab at one or both ends. Some railways, e.g., the Great Western...

  • Twin unit
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