Abstract: A steerable device for moving trailer type vehicles, for example in working and parking areas. The device includes an engine for driving at least one of the wheels, means for connecting the device to that part of a trailer type vehicle normally connected to the fifth wheel connection of a tractor unit, and tiller steering for turning a steerable wheel or wheels. The device also includes an air compressor driven by the engine and a flexible connection provided with a quick-release adaptor for coupling the air compressor to the braking system of a trailer type vehicle for releasing its brakes.