a automotive braking system for use on a vehicle for emergency stopping and parking comprising a mechanical brake caliper which exerts frictional stopping force on a brake rotor , the caliper being designed so as to provide a means of transferring mechanical force to the caliper pistons by means of a lever which transfers mechanical force to the piston through one or more apertures in the piston cylinders . the lever is operated by an actuator rod , which is engaged by a spring chamber having a heavy duty parking spring with and opposing force created by a variable pressure means , typically air or hydraulic . the system fails to a safe - mode mode wherein a loss of pressure opposing the parking spring results in the engagement of the braking system , bringing a moving vehicle to rest within a reasonable distance and holding a vehicle parked until such time the pressure can be restored .