Braking system, developed by AutoStop Corp., uses doppler-generated signals to reduce stopping distance of vehicle in danger of collision. Safety device acts on conventional controls of vehicle, provides backup where driver's reaction time is not adequate, and rapid deceleration is required to avoid collision. Actuation of controls to achieve deceleration is accomplished by two vacuum bellows, one mechanically linked to the brake pedal, another linked to throttle and accelerator. Braking action is initiated by driver. System discriminates between objects which present danger of collision, and false targets such as traffic in adjacent lanes and signposts.