The code provides test procedures and methods of calculating a brake rating from the data obtained for brakes used in highway commercial vehicles over 4.5 T (10 000 lbs) GVWR air and hydraulic. Some general correlation may be expected between brake ratings established by this means and those obtained from vehicle tests such as outlined in SAE J880. The brake rating power, kW (hp) calculated by conduct of this code is an arbitrary index of performance of the brake and drum when tested by this procedure and may be appreciably different from the values obtained by other techniques.