Parking brake

(a) Each passenger motor vehicle or motor vehicle with a G.V.W.R. of 10,000 lbs. or less having a hydraulic or any other type service brake system shall be equipped with a parking brake system which upon actuation by the operator shall be effective in applying braking action either directly or indirectly on at least two wheels. If the service brake system and the parking brake system are functionally connected in any way, they shall be so constructed that failure of any one part of the operating mechanism shall not leave the motor vehicle without parking ability on at least two wheels. The parking brake system shall be of the friction type with a solely mechanical means to retain engagement and shall be capable of holding the vehicle, when loaded to its G.V.W.R., to the limit of traction of the braked wheels in both forward and reverse directions on clean, dry, smooth Portland Cement Concrete pavement (or other surface with equivalent coefficient of surface friction) on grades and under conditions specified as follows: 1. 20% (11.3°) grade for any motor vehicle manufactured prior to January 1, 1976. 2. Any motor vehicle manufactured on or after January 1, 1976 shall meet the requirements of either part "a" or parts "b" and "c" below as applicable: a. 30% (16.7°) grade for any motor vehicle not equipped with a transmission control parking mechanism feature and any motor vehicle so equipped having the transmission parking mechanism disengaged. b. 30% (16.7°) grade for any motor vehicle equipped with a transmission control parking mechanism which is engaged simultaneously with the vehicle's parking brake. c. 20% (11.3°) grade for any motor vehicle equipped with a transmission control parking mechanism which is not engaged and the vehicle's parking brake is applied. (b) Each truck or bus having a hydraulic or any other type service brake system with a G.V.W.R. greater than 10,000 pounds shall have a parking brake system of a friction type with a solely mechanical means to retain engagement and shall be capable of holding the vehicle stationary, when loaded to its gross vehicle weight rating established by the manufacturer, in both forward and reverse directions on a 20% (11.3°) grade. (c) Each truck, bus or trailer equipped with an air brake system shall have a parking brake system capable of holding the vehicle or vehicle combination stationary when facing uphill and facing downhill on a smooth, dry Portland Cement Concrete roadway with a 20% (11.3°) grade, both (1) when loaded to its gross vehicle weight rating, and (2) at its unloaded vehicle weight plus 500 pounds (including driver and instrumentation). The parking brakes shall be applied by an energy source that is not affected by loss of air pressure or brake fluid pressure in the service brake system. Once applied, the parking brakes shall be held in the applied position solely by mechanical means.