A track system is arranged to be flush with the floor and a drive shaft is mounted for rotation beneath the level of the floor. A vehicle mounted on wheels is moved along the tracks by a drive wheel which extends downwardly from the bottom of the vehicle through an elongated slot in the floor and which contacts the drive shaft. The vehicle includes a bumper system which upon impact oscillates the drive wheel into a position which decellerates and stops the vehicle. A cam associated with the drive wheel selectively cooperates with a cam surface located beneath the floor level at a queuing station for oscillating the drive wheel into a position which decellerates and stops the vehicle. Means are also provided at the queuing station for positively holding the vehicle in a stopped position.
