Multiple unit facts for kids

A multiple unit is a type of train that can drive itself. This means it does not need a separate engine, called a locomotive, to pull or push it. Instead, each car, or many cars, have their own engines or motors. This design makes multiple units very flexible and efficient. They are used all over the world for passenger transport.

What is a Multiple Unit?

A multiple unit, often called an MU, is a train made of several cars that are all connected. Each car, or a group of cars, has its own power source. This is different from a traditional train, which has a separate engine pulling passenger cars or freight wagons.

Multiple units can be joined together to make longer trains. They can also be split into shorter trains. This flexibility helps train operators match the train's size to the number of passengers. For example, a short train might run during quiet times. A longer train can be used during busy rush hours.

Types of Multiple Units

There are two main types of multiple units, based on how they get their power:

Diesel Multiple Units (DMUs)

A Diesel multiple unit (DMU) has a diesel engine in one or more of its cars. This engine burns diesel fuel to create power. The power can then turn the wheels directly or generate electricity for electric motors. DMUs are often used on railway lines that do not have overhead electric wires or a third rail.

DMUs are common in many countries. They are good for routes that go through rural areas or where it is too expensive to install electric power systems. They are also used for long-distance journeys.

Electric Multiple Units (EMUs)

An Electric multiple unit (EMU) gets its power from electricity. This electricity usually comes from overhead wires or a special electrified rail, called a third rail. EMUs use electric motors to turn their wheels.

EMUs are very popular for city and suburban train services. They are often quieter and produce no pollution at the point of use. They can also accelerate and brake very quickly. This makes them ideal for routes with many stops. High-speed trains, like the Shinkansen in Japan or the ICE 3 in Germany, are often EMUs.

Why Use Multiple Units?

Multiple units offer several advantages over trains pulled by separate locomotives:

• Flexibility: As mentioned, they can be easily coupled or uncoupled. This allows operators to change train length quickly.
• Efficiency: Because power is spread out, multiple units can accelerate and brake faster. This saves time, especially on routes with frequent stops.
• No Need to Turn Around: Many multiple units have driver's cabs at both ends. This means the train does not need to be turned around at the end of a line. The driver can simply walk to the other end and drive in the opposite direction. This saves time at stations.
• Better Weight Distribution: Spreading the engines across the train means less weight on any single part of the track. This can reduce wear and tear on the railway lines.
• More Space: Without a separate locomotive, the entire length of the train can be used for passengers. This means more seats or standing room.

History of Multiple Units

The idea of multiple units began in the late 19th century. Early electric streetcars and trams often used a similar concept. However, the modern multiple unit system for full-sized trains was developed by Frank Sprague. In 1897, he created a system that allowed a single driver to control all the motors on a train. This was first used on the South Side Elevated Railroad in Chicago, USA.

This invention changed how trains were designed. It made it possible to build longer, more powerful electric trains. Soon, the idea was adapted for diesel trains too. Today, multiple units are a common sight on railways around the world.

Images for kids

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  A Deutsche Bahn ICE 3 EMU capable of up to 320 km/h (199 mph) in Rhineland-Palatinate, Germany

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  The Transwa Prospector DEMU capable of up to 200 km/h (124 mph) provides a passenger service between Perth and the mining town of Kalgoorlie in Australia.

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  South Side Elevated Railroad car #1, one of the cars that Frank Sprague converted to MU operation in Chicago

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  Metrorail 10M5 approaching Simon's Town station, Cape Town

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  A China Railway High-speed EMU

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  A N700 Series Shinkansen set in June 2008

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  Elektrichka on Yaroslavskiy Rail Terminal, Moscow

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  The RABe 523 is the most common multiple units on Switzerland, used by almost every S-Bahn.

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  Southern Class 377/2 377207 at Hemel Hempstead with a train from Milton Keynes Central to East Croydon

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  A double decker Sydney Trains B set

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  Indian Railways class Electric Multiple Unit

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  Indian Railways class Diesel Electric Multiple Unit

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  New Jersey transit Stadler GTW DMU used on the River Line

See also

In Spanish: Unidad múltiple para niños