Abstract: An accumulating conveyor formed by a series of self propelled pallets (18) running on a track (20), with non-contacting proximity detectors (24A, 24B) located on the front and rear of each pallet (18), and an on board control circuit (26) causing deenergization of the drive motor (22) when a stopped pallet (18) is detected ahead, or when barrier members (28, 30) are positioned ahead. Slow down, stopping and reversing of the drive may be controlled by side mounted photo detector switches (40A, 40B, 52A, 52B) activated by photo emitter devices (42A, 42B, 54A, 54B) mounted along the path of the pallets (18). A bilevel feed and return track (20A, 20B) may be traversed by the pallets (18), reversed to be driven in either direction, and either the forward or rear proximity switch (24A or 24B) activated by the control circuit (26) depending on the direction of travel of the car.