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). 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.