Power car

Acela Express power car

A power car is a railroad vehicle that is closely related to the locomotive. What differentiates the two is their construction or their use. A true locomotive can be physically separated from its train and does nothing but provide propulsion (and electricity for passenger trains). A power car, on the other hand, is frequently an integral part of its train. Some of its interior space may be used for holding passengers or cargo. Power cars are limited to passenger trains as their relative lack of versatility makes them unsuitable for hauling freight.

Nearly all high speed trains use power cars, frequently at both ends. An example of these are the Acela trainsets in use by Amtrak, which are built by Bombardier in Canada using technology licensed from France's Alstom. The twenty Acela trainsets operate between Washington, D.C. and Boston, Massachusetts. Each trainset consists of six passenger cars and two power cars. Another traditional example would be the older Intercity 125, made for and used by British Rail and several subsequent privatised bodies like Virgin Trains.

Multiple units (diesel or electric) usually have a mix of power cars and trailers, often with one of each in a pair which can be coupled to other pairs to form a larger train; see eg NZR FP class.