Multiple unit

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Perth and the mining town of Kalgoorlie in Australia

.

Multiple unit trains
Subtypes
Electric multiple unit Diesel multiple unit Motor coach Power car Push–pull train
Technology
Multiple-unit train control
By country
Britain (DMU) Britain (EMU) Ireland
v t e

A multiple-unit train or simply multiple unit (MU) is a self-propelled

.

Although multiple units consist of several carriages, single self-propelled carriages – also called

– are in fact multiple-units when two or more of them are working connected through multiple-unit train control (regardless if passengers can walk between the units or not).

History

Multiple-unit train control was first used in electric multiple units 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

) 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 the traction motors in the train are controlled in unison.

Design

Most MUs are powered either by

driving a generator producing electricity to drive traction motors.

A MU has the same power and traction components as a

, and another car carry the traction motors.

MU cars can be a motor or trailer car, it is not necessary for every one to be motorized. Trailer cars can contain supplementary equipment such as air compressors, batteries, etc.; they 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.

Passenger multiple units

Virtually all rapid-transit rolling stock, such as on the

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

Many

Freight multiple units

Multiple unit has been used, occasionally for freight traffic, such as carrying containers or for trains used for maintenance. The Japanese M250 series train has four front and end carriages that are EMUs, and has been operating since March 2004. The German CargoSprinter have been used in three countries since 2003.

Comparison to locomotive-hauled trains

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Advantages

Energy efficiency

They are more energy-efficient than locomotive-hauled trains. ^{[citation needed]}

Gradients

They have better adhesion, as more of the train's weight is carried on driven wheels, rather than the locomotive having to haul the dead weight of unpowered coaches.

Acceleration

They have a higher power-to-weight-ratio than a locomotive-hauled train since they don't have a heavy 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. Because of the

and higher adhesive-weight-to-total-weight ratio values, they generally have higher acceleration ability than locomotive-type trains and are favored in urban trains and metro systems for frequent start/stop routines.

Turnaround times

Most of them 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

.

Failure

Multiple units 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. As there are multiple engines/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 loads

They 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. They generally have rigid couplers instead of the flexible ones often used on locomotive-hauled trains. That means brakes/throttle can be more quickly applied without an excessive amount of jerk experienced in passenger coaches. In a locomotive-hauled train, if the number of cars is changed 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 2 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

Maintenance

It may be easier to maintain one locomotive than many self-propelled cars. 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 casualties than one with a locomotive (where the heavy locomotive would act as a "crumple zone").

Failure

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. However, if the train consists of more than one multiple unit they are often designed such that in the event of the failure of one unit others in the train can tow it in neutral if brakes and other safety systems are operational.

Idle trains

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.

Passage between units

It is difficult to have gangways between coupled units and still retain an aerodynamic leading front end. Because of this, there is usually no passage between high-speed coupled units, though lower-speed coupled units frequently have connections between coupled units.^{[citation needed]} This may require more crew members, so that ticket inspectors, for example, can be present in all of them. This leads to higher operating costs and lower use of crew resources. In a locomotive-hauled train, one crew can serve 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 unit, reducing efficiency.

Flexibility

Large locomotives can be used instead of small locomotives where 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-drawn 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 on multiple units two or more units have to be coupled. This is not so flexible.

Noise

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 DMUs.

Obsolescence

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

By country

Africa

Algeria

Algeria possesses 17 units of the Coradia El Djazaïr, a multiple unit train produced by Alstom. These units are similar to the French version of Régiolis, which belongs to the Coradia family.^[5]

South Africa

.

Gautrain, a commuter rail system in Johannesburg, operates with Bombardier Electrostar electric multiple units.

East Asia

China

The concept of multiple unit has entered the horizon of the Chinese since the 6th Speed-up Campaign of

(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 was the beginning of the general service of multiple unit trains in China's national railway system.

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

Japan

In Japan most passenger trains, including the high-speed Shinkansen, are of the multiple-unit (MU) type, with most locomotives now used solely in freight operations. Of the locomotive-hauled passenger services still in operation, the majority are tourist-oriented, such as the numerous steam-hauled trains operated seasonally on scenic lines throughout the country, as well as some of the luxury cruise trains.

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 MUs have advantages, encouraging their development in this country. Additionally, the mountainous terrain gives the MUs an advantage on grades steeper than those found in most countries, particularly on small private lines many of which run from coastal cities to small towns in the mountains.

Most long-distance trains in Japan were 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 Shinkansen development which optimized all of the EMU's efficiencies to maximize speed. It was introduced upon completion of the Tokaido Shinkansen (literally "new trunk line") in 1964. By the 1970s, locomotive traction was regarded as slow and inefficient, and its use is now mostly limited to freight trains.

From 1999, there have been development efforts in

between Tokyo and Osaka. The government has been pushing for the adoption of freight EMU technology on energy efficiency grounds in the hope that widespread adoption could assist in meeting CO₂ emissions targets. The effort has been principally targeted at express package shipping that would otherwise travel by road.

Europe

Belgium

The first EMUs have been introduced in Belgium in the 1930s. Several models have followed since then, such as the AM75.

Ireland

, the 2600-class, in 1951.

Russia

Yaroslavskiy Rail Terminal

, Moscow

Elektrichka (

.

Sweden

Swedish railroads have been privatized in steps for about 25 years, and today many different companies operate different types of multiple units. A majority of passenger trains today consists of multiple unit trains of which regional traffic exclusively use them.

Switzerland

The Swiss Federal Railways use many multiple units, mainly on regional lines (S-Bahn).

• Regional lines
  • RBDe 560
  • RABe 514
  • RABe 520 "Thurbo"
  • RABe 523 "FLIRT" and variants
  • RABe 511 "KISS"
• Inter-City lines
  • RABDe 500
    "ICN"
• International lines
  • ETR 610^[6]
  • RABe 501

United Kingdom

East Croydon

In the UK the use of modern diesel multiple units was pioneered in Northern Ireland,^[

trains.

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.

In

Northern Ireland Railways

(since 1967).

Oceania

Australia

The first multiple unis in Australia were the

Victoria. They were originally introduced as steam locomotive hauled carriages but were converted to electric traction from 1919 during Melbourne’s electrification project.^[7]

South Asia

India

Indian Railways has recently introduced a semi-high-speed EMU named Vande Bharat Express, capable of running at 183 km/h (114 mph). And it continues to use diesel and electrical multiple units on its national network. All suburban and rapid transit lines are served by EMUs.

Southeast Asia

Indonesia

Indonesia uses diesel since 1976 and electric MUs since 1925. Most of these MUs were built in Japan.

Philippines

The Manila Railroad Company (MRR) acquired its first multiple units in the 1930s. The locally-built MC class was initially powered by gasoline and was changed to diesel during World War II. Both the MRR and its successor, the Philippine National Railways (PNR), has since acquired various classes of diesel multiple units. All multiple units owned by MRR and all of the older MUs of the PNR were built by Japanese firms. On the other hand, its newer rolling stock were built in South Korea and Indonesia. There will also be DMUs that will be built in China.^[8]

The first electric multiple units were acquired in 1984 for the LRT Line 1 built by La Brugeoise et Nivelles in Belgium.^[9] The first EMUs to be used outside of rapid transit will enter service between 2021 and 2022.^[10]

North America

See also: Commuter rail in North America

Most trains in North America are locomotive-hauled and use Multiple Unit (MU) control to control multiple locomotives. The control system of the leading locomotive connects to the other locomotives so that the engineer's control is repeated on all the additional locomotives. The locomotives are connected by multi-core cables. The Railway Technical Website, vol. US Locomotive MU Control This does not make these locomotives MUs ^{[dubious – discuss]}for the purposes of this article. See locomotive consist.

However, commuters, rapid transit, and light rail operations make extensive use of MUs. Most^{[citation needed]} electrically powered trains are MUs.

The Southeastern Pennsylvania Transportation Authority (

New Jersey Transit service on the Northeast Corridor Line

is split between electric locomotives and EMUs.

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

Victoria - Courtenay train on Vancouver Island. DMU use in Canada has been resurrected in recent years, beginning with the opening of Union Pearson Express

in 2015.

While most DMUs need to comply with strict

New Haven north to St. Albans

to replace the less efficient diesel locomotive trainsets currently used.

MU streetcars were used in Toronto by the

PCC A-7 built by St. Louis Car Company and Canadian Car and Foundry.^[11] These two car units ran along the Bloor Street

route only beginning in 1950 and ceased operations after the opening of the Bloor–Danforth subway line in 1966. The A-7 units were later converted to single use.

See also

• Diesel multiple unit
• Power car
• Rail terminology
• Twin unit

References

1. ^ "Rulebook Master: Glossary of Railway Terminology, Train Working "Coupled in multiple - Traction units coupled to allow through controls by one driver"" (PDF). RSSB. Archived from the original (PDF) on 10 August 2018. Retrieved 28 September 2017.
2. ^ "Liverpool Overhead Railway Motor Coach Number 3, 1892". National Museums Liverpool. Retrieved 21 January 2011. 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. Sprague, Frank (18 January 1902). "Mr Sprague answers Mr Westinghouse". The New York Times
   . Retrieved 16 June 2012.
4. ^ "France unveils super-fast train", BBC News, 5 February 2008. Retrieved 5 February 2008.
5. ^ International2018-05-19T06:00:00+01:00, Railway Gazette. "By Coradia to Batna". Railway Gazette International. Retrieved 14 March 2024.{{cite web}}: CS1 maint: numeric names: authors list (link)
6. Eurocity
   lines
7. ^ Vincent, Peter J. (30 August 2007). "M – Sliding Door Suburban Motor Car". PJV's Website.
8. ^ "Chinese firm signs contract to supply trains for PNR Bicol project". 18 December 2019. Retrieved 1 October 2020.
9. ^ Satre, Gary (June 1998). "The Metro Manila LRT—A Historical Perspective" (PDF). Japan Railway & Transport Review. 16: 33–37. Archived (PDF) from the original on 18 May 2017.
10. ^ Valdez, Denise (21 May 2019). "DoTr prepares to award rolling stock contract". BusinessWorld. Manila. Retrieved 21 May 2019.
11. ^ Peter C. Kohler (25 June 2015). "The Post-War All-Electric PCC Cars (Classes A6-A8)". Transit Toronto.

Notes

Wikimedia Commons has media related to Multiple units.

• Martin, T. Commerford (1924). Kaempffert, Waldemar Bernhard (ed.). A Popular History of American Invention. Vol. 1. London; New York: Charles Scribner's Sons. pp. 122–123. Retrieved 11 March 2017 – via Internet Archive.