We examined state-specific and aggregate effects of U.S. legislation requiring the use of seat befts among front-seat motor vehicle occupants. Effects of compulsory seat belt 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-Tiao intervention analysis time-series methods. Because the new laws apply only to front-seat occupants, front-seat occupant fatalities were compared with: (1) rear-seat fatalities; (2) nonoccupant fatalities (motorcyclists, pedalcyclists, pedestrians); and (3) fatalities among front-seat occupants in neighboring states without compulsory seat belt use. Exposure to risk of crash involvement was controlled by analyzing fatality rates per vehicle mile traveled. Results revealed a statistically significant decline of 8.7% in the rate of front-seat fatalities in the first eight states with seat belt laws. The fatality rate declined 9.9% in states with primary enforcement laws and 6.8% in states with secondary enforcement only. Rates of rear-seat and nonoccupant fatalities did not change when the belt laws were implemented. Use of automobile safety belts reduces the probability of death in a motor vehicle crash by 30% to 50% (Evans, 1986; O'Day & Flora, 1982). To increase belt use, laws requiring their use were first implemented in Aus

Effects on motor vehicle crash involvement of raising the legal drinking age in Texas from 18 to 19 were examined, using an interrupted time-series design. Rates of single-vehicle-nighttime (SVN) and non-SVN crashes per 100,000 licensed drivers from 1978 through 1984 were examined for three levels of crash severity (serious injury, minor injury, property damage only) and four age groups (16-17, 18, 19-20, 21 and over). Resul's revealed significant reductions in SVN crashes for the 18-year-old target population across all levels of crash severity: serious injury, down 10.8 % ; minor injury, down 14.3% ; and property damage only, down 12.8%. In comparison, no significant changes in S/N crashes among drivers age 21 and over were found. When the effects of macroeconomic conditions on crash rates were controlled statistically, no change in the estimated effect of the legal age law was seen. It is clear that the l-year increase in legal age in Texas had a significant effect on youth crash involvement. Over half of the states in the U. S. lowered their minimum legal drinking age between 1970 and 1973. After these changes, several studies found significant increases in youth alcohol-related traffic crashes, although

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