Abstract: Apparatus for controlling movement of a heavy vehicle used in the mining and construction industries comprises a radar scanner (30) and an infra red detector (31) mounted at the rear of the vehicle for detecting a hazard in the path of the vehicle while reversing and a control system (10) responsive to the detection devices (30, 31) for controlling supply of air in a pneumatic supply system (11) of a retarder of the vehicle when a hazard is detected by the detection means (30, 31). The control system (10) includes driver operable apparatus (19, 23 and 40) for releasing the retarder.