Abstract: Track (2) serves the stations of a line. A plurality of pallets (1) travel on track (2). The track and the pallets have guide elements (4, 54, 55) working with one another. The track is bordered by at least one marginal driving belt (7). The pallet (1) has on at least one of its sides an element for gripping the belt (7). The gripping element has at least one heavy element (8, 18, 20) resting by gravity on belt (7) so that a movement of this belt (7) relative to pallet (1) produces by friction a movement of this heavy element (8, 18, 20), triggering the engagement of the gripping element of pallet (1) with belt (7).