Bilevel rail car

A bilevel car (American English) or double-decker coach (British English and Canadian English) is a type of rail car that has two levels of passenger accommodation as opposed to one, increasing passenger capacity (up to 57% per car in extreme cases).^[1]

The use of double-decker carriages, where feasible, can resolve capacity problems on a railroad, avoiding other options which have an associated infrastructure cost such as longer trains (which require longer station platforms), more trains per hour (which the signalling or safety requirements may not allow) or adding extra tracks besides the existing line.

Double deck trains are claimed to be more energy efficient,^[2] and may have a lower operating cost per passenger.^[3] A bi-level car may carry up to about twice as many as a normal car, if structure and loading gauges permit, without requiring double the weight to pull or material to build. However, a bi-level train may take longer to exchange passengers at each station, since more people will enter and exit from each car. The increased dwell time makes them most popular on long-distance routes which make fewer stops (and may be popular with passengers for offering a better view).^[1]

Double deck cars may not be usable in countries or on older railroad systems with low loading gauge, most notably the majority of the British railway network. In some countries such as the UK new lines are built to a higher than the existing structure gauge to allow the use of double-deck trains in future.^[4]