A trailer bus is a trailer vehicle designed specifically for the transportation of passengers (a bus). Trailer buses typically comprise one of two forms:
- a semi-trailer pulled by a tractor unit (in the same way as a semi-trailer truck). The tractor unit may either be a purpose-built unit designed specifically for operation with the trailer bus, or a regular conventional tractor unit.
- a full trailer pulled by a conventional bus, typically to provide extra capacity. Also referred to as a 'bus trailer'.
Although semi-trailer buses are now typically obsolete and have been retired, full trailer buses attached to conventional buses remain in use in limited applications around the world, including as tourist vehicles.