Preventing highway crashes by raising the legal minimum age for drinking: The Michigan experience 6 years later

Abstract

Results of a 6-year follow-up of previous research evaluating the effects of Michigan's December 1978 increase in the legal drinking age from 18 to 21 are reported. Earlier research demonstrated the immediate effect of Michigan's raised legal age in reducing motor vehicle crash involvement among young drivers. The current study examined 6 years of post-law traffic crash data, using Box-Jenkins intervention analysis methods to assess the long-term effects of the raised drinking age. Results revealed long-term ef- fects of the law similar to the initial effects identified earlier. Over the 6-year follow-up period, the rate of involvement in injury-producing single-vehicle nighttime crashes among drivers age 18-20 was 16 % lower than the level ex- pected, had the drinking age law not changed. Police-reported drinking driver crash involvement was down 19%. In contrast to many alcohol-im- paired driving countermeasures, the raised legal drinking age appears to have a long-term effect in reducing motor vehicle crash involvement among young drivers.