PURPOSE: To decrease the device pressure quickly as much as possible according to a predetermined plan in a case where excessive brake force is detected.

CONSTITUTION: This device includes a pedal operating valve 10, a pilot control insulating valve 26, an exhaust valve 16, a relay valve 12, an air pressure transducer 18, a wheel speed sensor, an electronic control unit(ECU) 20 and an air brake chamber associated with a brake actuator 14. During heavy braking operations, if braking of the vehicle wheel results in a wheel velocity change which exceeds a predetermined deceleration threshold, the pressure rise rate is further restricted in attempt to 'creep' up on the brake system pressure at which the lock condition is expected to occur. At another predetermined deceleration threshold, the brake system pressure is vented so that the brake system pressure decreases resulting in a reduction in brake force, thereby restoring the speed of the wheel. The speed-up rate is a function of the coefficient of friction of the road surface, load weight of the wheel and residual brake force remaining in the brake speed.