Static retardation force.
S5.6.1 Static retardation force. With all other brakes made inoperative, during a static drawbar pull in a forward or rearward direction, the static retardation force produced by the application of the parking brakes shall be:
(a) In the case of a vehicle other than a truck-tractor that is equipped with more than two axles, such that the quotient static retardation force/GAWR is not less than 0.28 for any axle other than a steerable front axle; and
(b) In the case of a truck-tractor that is equipped with more than two axles, such that the quotient static retardation force/GVWR is not less than 0.14.