Two of the major components of the highway transportation system--the highway and the vehicle--are not designed to be systematically compatible with each other. The problem of design incompatibilities can no longer be avoided because the variations in vehicle sizes, weights and configurations are rapidly increasing. Both the small car and the heavy truck, once the exception in the vehicle mix, now account for a substantial proportion of the mix;​ within ten years, the small car (minicompact, subcompact and compact) will be dominant among cars, and 25 percent of the total fleet will be trucks and buses. Design incompatibilities have persisted because auto and highway designers are not required to correlate their designs;​ changes to increase compatibility have traditionally only been made to the highway, a slow and costly process;​ highway designers do not, for the most part, design to performance standards;​ highway design elements are not required to be crash tested for performance;​ the Federal Highway Administration and the National Highway Traffic