The term multiple unit or MU is used to describe a self-propelling train unit capable of coupling with other units of the same or similar type and still being controlled from one cab. The term is commonly used to denote passenger trainsets that consist of more than one carriage A passenger car is a piece of railway rolling stock that is designed to carry passengers. The term passenger car can also be associated with a sleeping car, baggage, dining and railway post office cars, but single self-propelling carriages, or railcars 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 (carriage, car), with a driver's cab at one or both ends. Some railways, e.g. the Great Western Railway, used the term Railmotor. If it is able to pull a full train, it, can be referred to as multiple units if capable of operating with other units.

Multiple units are of three main types:

• Electric multiple unit An electric multiple unit or EMU is a multiple unit train consisting of more than one passenger carriages where all carriages in the train carry passengers, using electricity as the motive power. No locomotive is used as electric traction motors are incorporated within one or a number of the carriages (EMU)
• 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 (DMU)
• Diesel electric multiple units 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 (DEMU)

History and description

Multiple unit operation was made possible by the development of multiple-unit train control by the American ^ b. English is the de facto language of American government and the sole language spoken at home by 80% of Americans age five and older. Spanish is the second most commonly spoken language inventor An invention is a new composition, device, or process. An invention may be derived from a pre-existing model or idea, or it could be independently conceived in which case it may be a radical breakthrough. In addition, there is cultural invention, which is an innovative set of useful social behaviors adopted by people and passed on to others Franklin J. Sprague Frank Julian Sprague was an American naval officer and inventor who contributed to the development of the electric motor, electric railways, and electric elevators. His contributions were especially important in promoting urban development by increasing the size cities could reasonably attain (through better transportation) and by allowing greater. This allowed electrically Electricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning and static electricity, but in addition, less familiar concepts, such as the electromagnetic field and electromagnetic induction-powered rapid transit A rapid transit, metro, subway, underground, or elevated railway system is an electric passenger railway in an urban area with high capacity and frequency, and which is grade separated from other traffic. Rapid transit systems are typically either in underground tunnels or elevated above street level. Outside urban centres, rapid transit lines trains to be operated from a single driving position.

The first successful test of an MU on a working rapid transit system was in Chicago Chicago ( /ʃɨˈkɑːɡoʊ/ or /ʃɨˈkɔːɡoʊ/) is the largest city in both Illinois and the Midwest, and the third most populous city in the United States, with over 2.8 million living within the city limits. Its metropolitan area, commonly named "Chicagoland", is the 26th most populous in the world, home to an estimated 9.7 million, on the South Side "L", now part of the CTA Chicago Transit Authority, also known as CTA, is the operator of mass transit within the City of Chicago, Illinois and some of the suburbs. It is the second largest transit system in the United States and fourth largest in North America. The Chicago Transit Authority offers bus and rapid transit routes throughout the city, as well as to some Green Line.

Most MUs are powered either by a 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 during the final stage of compression. This is in contrast to spark ignition engines such as a petrol engine (known as a gasoline engine in North America) or gas engine (using a driving the wheels through a gearbox or hydraulic transmission (DMU 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), or by traction motors Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion, receiving their power through a live rail or overhead wire Overhead lines or overhead wires are used to transmit electrical energy to trams, trolleybuses or trains at a distance from the energy supply point. These overhead lines are known variously as (EMU). Diesel electric multiple units (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 Diesel locomotive is a type of railroad locomotive in which the prime mover is a Diesel engine. Several types have been developed, the principal distinction being in the means by which the prime mover's mechanical power is conveyed to the driving wheels.

A multiple unit trainset has the same power and traction components as a 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 century to distinguish, but instead of the components concentrating in one carbody, they are spread out on each car that makes up the set. Therefore these cars can only propel themselves when they are part of the set; thus making them semi-permanently coupled. For example, a DMU might have one car carry the prime mover 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. The term is also applied to engine-generator sets, where the engine is termed the prime and traction motors Traction motor refers to an electric motor providing the primary rotational torque of a machine, usually for conversion into linear motion, and another the engine for head end power generation; an EMU might have one car carry the pantograph A pantograph is a device that collects electric current from overhead lines for electric trains or trams. The term stems from the resemblance to pantograph devices for copying writing and drawings and 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 through the secondary winding. This varying magnetic, and another car carry the traction motors.

Virtually all rapid transit A rapid transit, metro, subway, underground, or elevated railway system is an electric passenger railway in an urban area with high capacity and frequency, and which is grade separated from other traffic. Rapid transit systems are typically either in underground tunnels or elevated above street level. Outside urban centres, rapid transit lines rolling stock, such as ones used in subway systems, are multiple unit trainsets, usually EMUs. Many 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 include 245 km/h (152 mph) for upgraded track and 295 km/h (183 mph) or faster for new track by the European Union. In Japan Shinkansen lines run at speeds in excess of 260 km/h (160 mph) and are rolling stocks are also multiple unit trainsets, such as the Japanese Japan is an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. The characters that make up Japan's name mean "sun-origin", which is why Japan is Shinkansen The Shinkansen , 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 210 km/h (130 mph) Tōkaidō Shinkansen in 1964, the now 2,459 km (1,528 mi) long network has expanded to link most major cities on the islands of Honshū and Kyūshū at speeds up to and the German A region named Germania, inhabited by several Germanic peoples, has been known and documented before AD 100. Beginning in the 10th century, German territories formed a central part of the Holy Roman Empire, which lasted until 1806. During the 16th century, northern Germany became the centre of the Protestant Reformation. As a modern nation-state, ICE 3 high-speed trains High-speed rail is a type of passenger rail transport that operates significantly faster than the normal speed of rail traffic. Specific definitions include 245 km/h (152 mph) for upgraded track and 295 km/h (183 mph) or faster for new track by the European Union. In Japan Shinkansen lines run at speeds in excess of 260 km/h (160 mph) and are.

Multiple units versus locomotive-hauled trains

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 grades, as much more of the train's weight (sometimes all of it) is carried on power-driven wheels, rather than suffer 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 for train services that have 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 subways 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 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 century to distinguish-hauled trains, has made the MU a major part of suburban Commuter rail, also called suburban rail, is a passenger rail transport service between a city center, and outer suburbs and commuter towns or other locations that draw large numbers of commuters—people who travel on a daily basis. Trains operate following a schedule, at speeds varying from 50 to 200 km/h . Distance charges or zone pricing may commuter rail services in many countries. MUs are also used by most rapid transit A rapid transit, metro, subway, underground, or elevated railway system is an electric passenger railway in an urban area with high capacity and frequency, and which is grade separated from other traffic. Rapid transit systems are typically either in underground tunnels or elevated above street level. Outside urban centres, rapid transit lines systems. This is no longer a problem for locomotive hauled trains due to increasingly widespread usage of push-pull trains.

• 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 smaller trains for different destinations.

• Reliability — Due to having multiple engines, or motors, the failure of one engine does not prevent the train from continuing its journey. A locomotive-drawn train A train is a connected series of vehicles for rail transport that move along a track to transport freight or passengers from one place to another. The track usually consists of two rails, but might also be a monorail or maglev guideway typically only has one power unit whose failure will disable the train. 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.

• Safety — Multiple units normally have completely independent braking systems on all cars meaning the failure of the brakes on one car does not prevent the brakes from operating on the other cars.

• Axle load — Multiple units have lighter axle loads, allowing operation on lighter tracks, where locomotives are 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 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 number of cars is increased in order to meet the demand, acceleration and braking performance drops. This calls for the necessity that, the performance calculations are to be done taking the heaviest train composition into account. This may sometimes lead 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.^{[citation needed]}

• 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').^{[citation needed]}

• 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.^{[citation needed]}

• 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 for use in passenger transportation.^{[citation needed]}

• Gangways - It is difficult to have gangways between coupled sets, and still retain an aerodynamic leading front end. Because of this fact, generally there is no passage between high-speed coupled sets.^{[citation needed]}

• 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. However, it 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.^{[citation needed]}

• Crew resources - When two or more multiple units are coupled; since there would be no passage between them, crew (i.e. ticket inspectors) should 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 unless limits of individual workload are not exceeded.^{[citation needed]}

• Buffet or restaurant cars - The presence of buffet or restaurant cars may create a problem when two or more multiple units are coupled together. If there is no passage between the coupled sets, then buffets and restaurants should be present in all the sets individually. This reduces efficiency. In a locomotive - hauled train, one single buffet or restaurant can serve the entire train regardless of number of cars in the train, until its serving capacity is exceeded.^{[citation needed]}

• 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 DMUs 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.^{[citation needed]}

• Obsolescence cycles - Separating the motive power from the payload-carrying cars means that either can be replaced when obsolete without affecting the other.^{[citation needed]}

Features

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 some supplemental equipment such as air compressors, batteries, etc.

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. This is the case with NJ Transit The New Jersey Transit Corporation is a statewide public transportation system serving the state of New Jersey, United States, and Orange and Rockland counties in New York. It operates bus, light rail, and commuter rail services throughout the state, notably connecting to major commercial and employment centers both within the state and in the Arrows, Metro-North Railroad (New York) EMUs. However, other EMUs can be driven/controlled only from dedicated Cab cars. Among such EMUs are the former Russian ER2, ER9, German classes 423-426, etc.

Well-known examples of MUs are the Japanese Shinkansen The Shinkansen , 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 210 km/h (130 mph) Tōkaidō Shinkansen in 1964, the now 2,459 km (1,528 mi) long network has expanded to link most major cities on the islands of Honshū and Kyūshū at speeds up to and the last generation German ICE The Intercity-Express — in Austria, Denmark and Switzerland: InterCityExpress ; abbreviation: ICE (German pronunciation: [iːtseːˈʔeː]) — 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. The brand. Most trains in the Netherlands The Netherlands (pronounced /ˈnɛðɚləndz/ ; Dutch: Nederland, pronounced [ˈneːdərlɑnt] ( listen)) is a constituent country of the Kingdom of the Netherlands, located in North-West Europe. It is a parliamentary democratic constitutional monarchy. The Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany and Japan Japan is an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. The characters that make up Japan's name mean "sun-origin", which is why Japan is are MUs, making them suitable for use in areas of high population density. A new high-speed MU, the AGV, was unveiled by France's Alstom Alstom is a large French multinational conglomerate which holds interests in the power generation and transport markets. According to the company website, in the years 2007-'08 Alstom had annual sales of over €16.9 billion, and employed more than 81,500 people in 70 countries. Alstom's headquarters are located in Levallois-Perret, near Paris on February 5, 2008. It has a claimed service speed of 360 km/h.^[1]

By country

Ireland

CIE introduduced its first DMUs, the 2600-class, in 1951.

Japan

In Japan Japan is an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. The characters that make up Japan's name mean "sun-origin", which is why Japan is, most passenger train vehicles including the high-speed Shinkansen The Shinkansen , 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 210 km/h (130 mph) Tōkaidō Shinkansen in 1964, the now 2,459 km (1,528 mi) long network has expanded to link most major cities on the islands of Honshū and Kyūshū at speeds up to are multiple unit type except for small numbers of overnight sleeper trains — very few passenger trains are now locomotive type. Well over 90 per cent of passenger trains are currently MU type.

Japan is a country of high population density and large number of railway passengers in a relatively small urban area, 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.

Most long distance trains in Japan had been operated by locomotives until the 1950s The 1950s was the decade that began on January 1, 1950 and ended on December 31, 1959. The decade was the sixth decade of the 20th century. By its end, the world had largely recovered from World War II and the Cold War developed from its modest beginning in the late 1940s to a hot competition between the United States and the Soviet Union by the, 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 development of the MU type high-speed train, the Shinkansen, in 1964 1964 (MCMLXIV, "nineteen sixty-four", "nineteen hundred sixty-four", or "one thousand, nine hundred (and) sixty-four") was a leap year starting on Wednesday (link will display full calendar) of the Gregorian calendar. Later on, locomotive type trains have been regarded as slow and inefficient, and their use has significantly decreased in Japan.

Russia

Elektrichka (Russian: электри́чка, Ukrainian: електри́чка, elektrychka) is an informal word for elektropoezd (Russian: электропо́езд), a Soviet or post-Soviet regional (mostly suburban) electrical multiple unit passenger train. Elektrichkas are widespread in Russia, Ukraine and some other countries of the former Soviet Union. The first elektrichka ride occurred in August 1929 between Moscow and Mytishchi.

United Kingdom

In Northern Ireland 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 (1948-1966) and Northern Ireland Railways (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 and Voyager families, and the brand new Olympic Javelin 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. However, commuters, rapid transit, and light rail 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 service on the Northeast Corridor Line is split between electric locomotives and EMUs.

M2, M4, M6 and future M8 EMUs which operate on the New Haven Line of Metro-North Railroad, are “dual mode” meaning they can draw power from either the third rail or from overhead lines. This allows operation under the wires between Pelham, NY and New Haven, CT, 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. EMUs are used on AMT'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) and Canada. These operations generally survived longer in Canada, but several were abandoned in the VIA Rail cutbacks of the early 1990s. One that survives is The Mahalat on Vancouver Island.

DMUs are used on the RiverLINE in New Jersey. Currently Colorado Railcar is demonstrating an FRA Crash Compliant DMU in the United States. NJ Transit has experimented with this DMU on the Princeton Branch 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 to replace the less efficient diesel locomotive trainsets currently used.

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 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.

Steam

The United Kingdom had various examples of Autotrain on branch lines, whereby a steam locomotive could be controlled by driving trailers at the opposite end of the train, or in the middle. This avoided the need to run around the locomotive at the terminals. These autotrains were limited to about two carriages.

References

1. ^ "France unveils super-fast train", BBC News, 2008-02-05. Retrieved on 2008-02-05.

See also

Categories

• Locomotive
• Rail motor coach
• Railbus / Railcar

General

• Rail terminology
• Pacer (train) units.
• Hybrid locomotive

Categories: Multiple units | Electric rail transport

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