Abstract: A braking system for a wheeled vehicle includes a pressurized air source (63), an air actuated wheel braking device (51, 59), an operator control (49, 61) for commanding the supply of air to the braking device, an electronic control (19) which responds to vehicle speed and wheel speed to selectively invoking an antilock mode of braking. A control valve (37, 55) responds to the electronic control (19) and the operator control (49, 61) to selectively control the supply of air from the source to the braking device. In the antilock mode, the control valve is initially enabled to release braking pressure and thereafter alternately enabled and disabled to maintain braking pressure at a substantially constant reduced pressure, and subsequently alternately enabled and disabled at a reduced ratio of enabled duration to disabled duration to rebuild braking pressure.