Retardation force can be calculated as follows:
(a) To own a trailer made to tow other vehicle equipped with heavens brake system, the pressure differential involving the handle range type in coupling and a great 50-cubic-inches attempt tank connected to the manage range returns coupling shall not meet or exceed the prices given inside the step three.5(a) (1), (2), and (3) within the criteria given inside the 3.5(b) (1) through (4):