Effects of mandatory seatbelt laws on traffic fatalities in the United States

Wagenaar, Alexander C.; Maybee, Richard G.; Sullivan, Kathleen P.

Affiliations

¹The University of Michigan Transportation Research Institute Injury Analysis and Prevention Group, United States

Abstract

We examined state-specific and aggregate effects of U.S. legislation requiring the use of seatbelts among front-seat motor vehicle occupants. Effects of compulsory seatbelt use on the number of occupants fatally injured in traffic crashes were examined in the first eight states adopting such laws.

Monthly data on crash fatalities between January 1976 and June 1986 were analyzed using Box-Jenkins intervention analysis time-series methods. Because the new laws only apply to front-seat occupants, front-seat occupant fatalities were compared with; (l) rear-seat fatalities; (2) nonoccupant fatalities (motorcyclists, pedalcyclists, pedestrians); and (3) fatalities among front-seat occupants in neighboring states without compulsory seatbelt use. Exposure to risk of crash involvement was controlled by analyzing fatality rates per vehicle mile traveled.

Results revealed a statistically significant decline in the rate of front-seat fatalities of 8.7% in the first eight states with scatbelt laws. The fatality rate declined 9.9% in states with primary enforcement laws and 6.8% in states limited to secondary enforcement only. Rates of rear-seat and nonoccupant fatalities have not changed since the belt laws were implemented.

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