Abstract: The device controls the speed of a driverless vehicle by way of a cam having an acceleration surface and a deceleration surface for contact with a cam follower on the driverless vehicle. The cam is mounted for reciprocation in a horizontal direction between an operative position wherein the deceleration surface will cause a driverless vehicle to stop and an inoperative position wherein the cam will not cause such vehicle to stop.

Abstract: A retractable wheel chock assembly for railway wagons comprises the combination of a wheel chock (12) designed to act on the flange of a wagon wheel, and a friction brake (36) attached to the wheel chock and sliding along a guide rail (3) mounted just outside the railway track (4) on which the wagon is running. The wheel chock (12) is at one end of a cantilever arm (10) that can be swung out over the railway track or inwardly over the guide rail. Both the cantilever arm and the friction brake are mounted on a carriage (1) that is movable longitudinally of the guide rail, and a linkage between the arm and the brake ensures that the brake is actuated in response to the reaction force of the wagon wheel on the wheel chock. The wheel chock may be extended over the railway track, advanced along the track into abutment with a wagon wheel and braked, all in a single operative movement.