Electric multiple unit

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A Liverpool Overhead Railway carriage in the Museum of Liverpool. The first EMUs in 1893. Liverpool Overhead Railway carriage, Museum of Liverpool-2.jpg
A Liverpool Overhead Railway carriage in the Museum of Liverpool. The first EMUs in 1893.
The prototype unit of JNR 201 series on public display at Harajuku Station in Tokyo, 13 May 1979. Next to it, a Yamanote Line's 103 series train can be seen passing through 201 900 prototype.JPG
The prototype unit of JNR 201 series on public display at Harajuku Station in Tokyo, 13 May 1979. Next to it, a Yamanote Line's 103 series train can be seen passing through
DART 8500 class commuter EMU at Howth Junction railway station, Ireland. Howth Junction railway station in 2007.jpg
DART 8500 class commuter EMU at Howth Junction railway station, Ireland.
A high-speed EMU CR400BF-G operated by China Railway High-speed at Beijing Chaoyang railway station CR400BF-G-5168@IFP (20210128114409).jpg
A high-speed EMU CR400BF-G operated by China Railway High-speed at Beijing Chaoyang railway station

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. An EMU is usually formed of two or more semi-permanently coupled carriages, but electrically powered single-unit railcars are also generally classed as EMUs. The great majority of EMUs are passenger trains, but versions also exist for carrying mail.


EMUs are popular on commuter and suburban rail networks around the world due to their fast acceleration and pollution-free operation. [1] Being quieter than diesel multiple units (DMUs) and locomotive-hauled trains, EMUs can operate later at night and more frequently without disturbing nearby residents. In addition, tunnel design for EMU trains is simpler as no provision is needed for exhausting fumes, although retrofitting existing limited-clearance tunnels to accommodate the extra equipment needed to transmit electric power to the train can be difficult.


Multiple unit train control was first used in the 1890s.

The Liverpool Overhead Railway opened in 1893 with two-car electric multiple units, [2] controllers in cabs at both ends directly controlling the traction current to motors on both cars. [3]

The multiple unit traction control system was developed by Frank Sprague and first applied and tested on the South Side Elevated Railroad (now part of the Chicago 'L') in 1897. In 1895, derived from his company's invention and production of direct current elevator control systems, Frank Sprague invented a multiple unit controller for electric train operation. This accelerated the construction of electric traction railways and trolley systems worldwide. Each car of the train has its own traction motors: by means of motor control relays in each car energized by train-line wires from the front car all of the traction motors in the train are controlled in unison.


Metro-North Railroad M8 married pairs in Port Chester, New York MNCRR M-8 at NEC Port Chester.jpg
Metro-North Railroad M8 married pairs in Port Chester, New York

The cars that form a complete EMU set can usually be separated by function into four types: power car, motor car, driving car, and trailer car. Each car can have more than one function, such as a motor-driving car or power-driving car.

On third rail systems, the outer vehicles usually carry the pick up shoes with the motor vehicles receiving the current via intra-unit connections.

Many modern two-car EMU sets are set up as twin or "married pair" units. While both units in a married pair are typically driving motors, the ancillary equipment (air compressor and tanks, batteries and charging equipment, traction power and control equipment, etc.) are shared between the two cars in the set. Since neither car can operate without its "partner", such sets are permanently coupled and can only be split at maintenance facilities. Advantages of married pair units include weight and cost savings over single-unit cars (due to halving the ancillary equipment required per set) while allowing all cars to be powered, unlike a motor-trailer combination. Each car has only one control cab, located at the outer end of the pair, saving space and expense over a cab at both ends of each car. Disadvantages include a loss of operational flexibility, as trains must be multiples of two cars, and a failure on a single car could force removing both it and its partner from service.

As high speed trains

Some of the more famous electric multiple units in the world are high-speed trains: the Italian Pendolino and Frecciarossa 1000, Shinkansen in Japan, the China Railway High-speed in China, ICE 3 in Germany, and the British Rail class 395 Javelin. The retired New York–Washington Metroliner service, first operated by the Pennsylvania Railroad and later by Amtrak, also featured high-speed electric multiple-unit cars, known as the Budd Metroliner.

Fuel cell development

EMUs powered by fuel cells are under development. If successful, this would avoid the need for an overhead line or third rail. An example is Alstom’s hydrogen-powered Coradia iLint. [4] The term hydrail has been coined for hydrogen-powered rail vehicles.

Battery electric multiple unit

Many battery electric multiple units are in operation around the world, with the take up being strong. Many are bi-modal taking energy from onboard battery banks and line pickups such as overhead wires or third rail. In most cases the batteries are charged via the electric pickup when operating on electric mode.

Comparison with locomotives

EMUs, when compared with electric locomotives, offer: [5]

Electric locomotives, when compared to EMUs, offer:

See also

Related Research Articles

<span class="mw-page-title-main">Locomotive</span> Self-propelled railway vehicle

A locomotive or engine is a rail transport vehicle that provides the motive power for a train. If a locomotive is capable of carrying a payload, it is usually rather referred to as a multiple unit, motor coach, railcar or power car; the use of these self-propelled vehicles is increasingly common for passenger trains, but rare for freight.

<span class="mw-page-title-main">Multiple unit</span> Self-propelled train

A multiple-unit train or simply multiple unit (MU) is a self-propelled train composed of one or more carriages joined together, which when coupled to another multiple unit can be controlled by a single driver, with multiple-unit train control.

<span class="mw-page-title-main">Railcar</span> Self-propelled railway vehicle designed to transport passengers

A railcar 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 railway companies, such as the Great Western, termed such vehicles "railmotors".

<span class="mw-page-title-main">Diesel locomotive</span> Locomotive powered by a diesel engine

A diesel locomotive is a type of railway locomotive in which the prime mover is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is conveyed to the driving wheels.

<span class="mw-page-title-main">Electric locomotive</span> Locomotive powered by electricity

An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a battery or a supercapacitor. Locomotives with on-board fuelled prime movers, such as diesel engines or gas turbines, are classed as diesel-electric or gas turbine-electric and not as electric locomotives, because the electric generator/motor combination serves only as a power transmission system.

<span class="mw-page-title-main">Multiple-unit train control</span>

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—with only a control signal transmitted to each unit. This contrasts with arrangements where electric motors in different units are connected directly to the power supply switched by a single control mechanism, thus requiring the full traction power to be transmitted through the train.

<span class="mw-page-title-main">Traction motor</span> Electric motor for vehicle propulsion

A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric or hydrogen vehicles, elevators or electric multiple unit.

The Lancashire and Yorkshire Railway (LYR) built suburban electric stock for lines in Liverpool and Manchester. The line between Liverpool to Southport began using electric multiple units (EMUs) on 22 March 1904, using a third rail 625 V DC. Additional trains were later built for this route, and in 1913 incompatible stock for the route to Ormskirk. Lightweight units were built to run on the Liverpool Overhead Railway.

<span class="mw-page-title-main">British Rail Class 313</span> 1976 British electric trains

The British Rail Class 313 is a dual-voltage electric multiple unit (EMU) train built by British Rail Engineering Limited's Holgate Road carriage works between February 1976 and April 1977. They were the first production units that were derived from British Rail's 1971 prototype suburban EMU design which, as the BREL 1972 family, eventually encompassed 755 vehicles over five production classes. They were the first second-generation EMUs to be constructed for British Rail and the first British Rail units with both a pantograph for 25 kV 50 Hz AC overhead lines and contact shoe equipment for 750 V DC third rail supply. They were, additionally, the first units in Britain to employ multi-function automatic Tightlock couplers, which include electrical and pneumatic connections allowing the coupling and uncoupling of units to be performed unassisted by the driver whilst in the cab.

<span class="mw-page-title-main">British Rail Class 310</span>

The British Rail Class 310 was a slam-door, alternating current (AC) electric multiple unit (EMU) introduced in 1965 as part of the West Coast Main Line electrification project. They were initially classified as Class AM10 units before the introduction of the TOPS classification system. Constructed at BR's Derby Carriage and Wagon Works. They consisted of four carriages - a second class driving trailer, a second class trailer, a second class motor car and a composite driving trailer. The maximum speed was 75 miles per hour. A glass partition behind the driver's cab enabled passengers in the leading and rear coaches to view the line ahead or behind.

<span class="mw-page-title-main">Tasmanian Government Railways X class</span> Class of 32 Australian Bo′Bo′ diesel-electric locomotives

The X class is a class of diesel locomotives built by English Electric for the Tasmanian Government Railways between 1950 and 1952. They were the first class of diesel locomotive to enter mainline service on a Government-owned railway in Australia.

<span class="mw-page-title-main">London Underground battery-electric locomotives</span>

London Underground battery-electric locomotives are battery locomotives used for hauling engineers' trains on the London Underground network where they can operate when the electric traction current is switched off. The first two locomotives were built in 1905 for the construction of the Great Northern, Piccadilly and Brompton Railway, and their success prompted the District Railway to buy two more in 1909, which were the only ones built to the loading gauge of the subsurface lines. Following this, a number of battery vehicles were built by converting redundant motor cars, with the batteries placed in the unused passenger compartment. One exception to this was made by the City and South London Railway, who used a trailer car to hold the batteries, and wired them to a separate locomotive.

<span class="mw-page-title-main">British electric multiple units</span> Trains without locomotives, in the European country

An electric multiple unit (EMU) is an electric train capable of operating in multiple with other EMUs that does not have a separate locomotive, typically passenger trains with accommodation in every vehicle and a driving position at each end. The term can also be used to describe a train such as the Advanced Passenger Train that was a permanent formation with a non-driving power car. As of December 2010 two-thirds of the passenger carriages in Britain are formed in EMUs.

<span class="mw-page-title-main">British Rail Class 306</span>

The British Rail Class 306 was a type of electric multiple unit (EMU) introduced in 1949. It consisted of 92 three-car trains which were used on the Great Eastern Main Line between Shenfield and London Liverpool Street.

<span class="mw-page-title-main">Rhodesia Railways class DE2</span> Zimbabwean diesel locomotive class

Rhodesia Railways class DE2 are a type of diesel locomotive built for operations on Rhodesia Railways in the 1950s. The first entered service on 22 June 1955.

<span class="mw-page-title-main">Control car</span> Unpowered railway or tramway car with a drivers cab

A control car, cab car, control trailer, or driving trailer is a non-powered rail vehicle from which a train can be operated. As dedicated vehicles or regular passenger cars, they have one or two driver compartments with all the controls and gauges required to remotely operate the locomotive, including exterior locomotive equipment such as horns, bells, ploughs, and lights. They also have communications and safety systems such as GSM-R or European Train Control System (ETCS). Control cars enable push-pull operation when located on the end of a train opposite its locomotive by allowing the train to reverse direction at a terminus without moving the locomotive or turning the train around.

<span class="mw-page-title-main">ER2 electric trainset</span> Electric multiple unit

ER2 electric trainset is a DC electric multiple unit which was in production by the Railroad Machinery Plants of Riga from June 1962 to mid-1984. It was essentially an improvement of the ER1 design, featuring footboards for low platforms, and aprons for high platforms, as well as improved electrical equipment and minor changes to the bodywork. Since the mid-1960s, the ER2 has been the most widely used type of suburban train in the Soviet Union and its successor states.

<span class="mw-page-title-main">South African Class 5E1, Series 1</span>

The South African Railways Class 5E1, Series 1 of 1959 was an electric locomotive.

<span class="mw-page-title-main">EMU100 series</span> Former passenger train in Taiwan

The Taiwan Railway EMU100 series was a set of rail cars fabricated by British Rail Engineering Limited and the General Electric Company in 1976 that has operated in Taiwan. The alternating current electric multiple unit (EMU) fleet entered full squadron service in 1979, and was withdrawn from service in 2009. This class of railcars were the first to operate on the electric Tzu-Chiang Express. Due to the unit's British origin, rail buffs have variously nicknamed them "British Girl", "British Lady", or "British Grandma".

A multiple-unit train or simply multiple unit (MU) is a self-propelled train composed of one or more carriages joined together, which when coupled to another multiple unit can be controlled by a single driver, with multiple-unit train control. Although multiple units consist of several carriages, single self-propelled carriages such as railbuses and trams – are in fact multiple-units when two or more of them are working connected through multiple-unit train control.


  1. N. K. De (2004). Electric Drives. PHI Learning Pvt. Ltd. 8.4 "Electric traction", p.84. ISBN   9788120314924.
  2. "Liverpool Overhead Railway motor coach number 3, 1892". National Museums Liverpool . Retrieved 2011-01-21. This is one of the original motor coaches which has electric motors mounted beneath the floor, a driving cab at one end and third class accommodation with wooden seats.
  3. Frank Sprague (18 January 1902). "Mr Sprague answers Mr Westinghouse". The New York Times . Retrieved 16 June 2012.
  4. "What you need to know about Alstom's hydrogen-powered Coradia iLint - Global Rail News". globalrailnews.com. 24 October 2017.
  5. Hata, Hiroshi. "What Drives Electric Multiple Units?" (PDF). Railway Technology Today. Archived from the original (PDF) on 1 November 2021. Retrieved 13 March 2022.