page_title: Electric multiple unit
section_title: Types
hierarchical_section_title: Electric multiple unit / Types
caption_attribution_description: English: w:British Rail Class 380 unit 380108 at w:Haymarket railway station platform 0
context_page_description: 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 parcels and mail.
  EMUs are popular on commuter and suburban rail networks around the world due to their fast acceleration and pollution-free operation. Being quieter than diesel multiple units 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.
context_section_description: 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.
  A power car carries the necessary equipment to draw power from the electrified infrastructure, such as pickup shoes for third rail systems and pantographs for overhead systems, and transformers.
  Motor cars carry the traction motors to move the train, and are often combined with the power car to avoid high-voltage inter-car connections.
  Driving cars are similar to a cab car, containing a driver's cab for controlling the train.  An EMU will usually have two driving cars at its outer ends.
  Trailer cars are any cars that carry little or no traction or power related equipment, and are similar to passenger cars in a locomotive-hauled train.
  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 2-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.
caption: A First ScotRail Class 380 EMU at Haymarket in Edinburgh, Scotland
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