Abstract: A fluid pressure operated braking system of the kind which includes an electrical system which is associated with wheels of the vehicle and arranged to regulate the braking force applied to the associated wheels, and which is operable automatically to effect release of a brake acting on the associated wheels when the deceleration thereof exceeds a predetermined amount and to re-apply the brake when the angular velocity of the respective wheels approaches that at which the periphery of the wheel rolls on the road surface without slipping. The system senses the time for which the brake is released and if the sensed time is greater than a predetermined time, the electrical system is rendered inoperative to permit re-application of the brake.