Intermixing of Tractors and Trailers Equipped with Existing and FMVSS 121 Braking Systems

There are a number of factors affecting the braking stability on tractor-semitrailer combination vehicles when intermixing new and existing braking systems. The changes in the stability of combination vehicles caused by the differences in brake performance levels, brake torque utilization, and brake system response of new and existing systems will be evaluated. The new and the existing systems will be pictorially compared and discussed to clarify the features and performance parameters required on the new equipment which must work in conjunction with pre-FMVSS 121 brake systems.