The 1982 Surface Transportation Assistance Act (STAA): Implications of relaxed truck weight and size limits for highway safety

Abstract

This paper examines the highway safety implications of the 1982 Surface Transportation Assistance Act (STAA) which, among its provisions, increased minimum truck lengths and maximum truck widths; required states to allow twin trailers; and barred states from reducing existing weight and size limits if these exceeded the limitations specified in the STAA. Evidence is presented that increases in an index of truck fleet size deteriorate highway safety, all else constant. A 1% increase in this index increases the system-wide fatality rate by 0.31%. Although the relationship between highway safety and size of trucking fleet has implications for policies aimed at achieving productivity gains through further increases in weight and size limits, the specific provisions embodied in the STAA had a small beneficial effect on this relationship. Relative to the pre-law environment, highway safety in the post-law environment was slightly less sensitive to changes in size of the trucking fleet.