An engineering analysis of tractor-semitrailer braking is presented in terms of the utilization of available tire-roadway friction. The effects of load transfer on the tandem axle suspension upon braking performance are discussed. The physical relations are derived that allow the determination of an improved brake force distribution among the axles of the combination as a function of the geometric and loading configuration. Tractor-semitrailers operating on our highways have braking efficiencies as low as 60%. Increase in braking performance can be expected provided the brake force distribution is improved. Eliminating the front brakes without changing the base line distribution has an unfavorable effect upon the braking performance of the combination.