A steerable, retractable power drive unit (SRPDU) is provided for installation into a transport vehicle for moving cargo in mutually perpendicular directions, such as a doorway are where containers need to move both laterally and longitudinally in a cargo vehicle. The SRPDU rotates upon application of an external command, to orient the drive unit in the required direction and to drive the cargo containers. The SRPDU comprises a stationary support (1010) for fixedly attaching to a vehicle structure and a rotating support (1020) rotatably mounted to the stationary support. A drive
assembly is movably mounted to the rotating support, the drive
assembly comprising a roller (120) and a first electronically controlled
electric motor for rotating the roller. A lift
assembly (150) mounted to the drive assembly has a second electronically controlled
electric motor for moving the drive assembly relative to the rotating support from a retracted position substantially within the rotating support to an extended position with the roller in driving
abutment against the cargo. A rotation drive assembly has a third electronically controlled
electric motor (1030) on the rotating support for rotating the rotating support relative to the stationary support. An
electronic controller (1060) controls the first, second and third motors.