Official statistics of motor vehicle fatality data have indicated that alcohol involvement in fatal crashes has declined substantially in Japan since 1970. The national campaign against drunken driving in Japan provides a natural experiment in which to test the predictions of deterrence theory. Utilizing official data over the 1960-1995 period, we report conclusive evidence that 1970s legislation is having a measurable and long-term effect on alcohol-related motor vehicle fatalities. Enactment of the lower legal blood alcohol limit with a combination of other severe sanctions has been more desirable in the prevention of alcohol-related fatalities in the long term as shown in this study. Further extensive research is necessary to investigate performance at the lower legal limit in other societies in order to inspire a strong "international lobby" to support the reduced legal blood alcohol limit for drivers all over the world, as there is no doubt that a reduction in alcohol-impaired driving will result in a substantial savings of human lives and resource worldwide.