Summary

Most states make it illegal for someone to drive with a blood alcohol concentration (BAC) of .10--the level at which a person's blood contains 1/10th of one percent alcohol. However, 16 states have more stringent laws setting the limitation at .08 BAC. In 1998, the Clinton administration endorsed a bill that would have required all states to enact and enforce .08 BAC laws or face cuts in federal highways funds. GAO found that the evidence does not conclusively establish that .08 BAC laws, by themselves, reduce the number and the severity of alcohol-related crashes. There are, however, strong indications that .08 BAC laws, in combination with other drunk driving laws (particularly license revocation laws), sustained public education and information efforts, and vigorous and consistent enforcement can save lives. Until recently, only four published studies examined the effectiveness of BAC laws in five states, and, although the National Highway Traffic Safety Administration characterized the studies as conclusively establishing that .08 BAC laws by themselves were effective, the studies had limitations. In April 1999, three additional studies were released that were more comprehensive and showed many positive results but also fell short of providing conclusive evidence that .08 BAC laws were, by themselves, responsible for reducing alcohol-related crashes and fatalities.

GAO noted that: (1) overall, the evidence does not conclusively establish that .08 BAC laws, by themselves, result in reductions in the number and severity of alcohol-related crashes; (2) there are, however, strong indications that .08 BAC laws in combination with other drunk driving laws, sustained public education and information efforts, and vigorous and consistent enforcement can save lives; (3) for example, while two studies have concluded that California's .08 BAC law was not directly associated with the decline in drunk driving deaths the state experienced in the early 1990s, these studies found that the .08 BAC law was effective when paired with the state's license revocation law, which took effect six months later; (4) until recently, only four published studies examined the effectiveness of .08 BAC laws in five states and, while NHTSA characterized the studies as conclusively establishing that .08 BAC laws by themselves were effective, the studies had limitations and raised methodological concerns calling their conclusions into question or reported mixed results; (5) in April 1999, three additional studies were released that were more comprehensive and showed many positive results but nevertheless fell short of providing conclusive evidence that .08 BAC laws were, by themselves, responsible for reductions in alcohol-related crashes and fatalities; (6) it is difficult to accurately predict how many lives would be saved if all states enacted .08 BAC laws because whether a state sees reductions after enacting a .08 law depends on a number of factors, including the degree to which the law is publicized, how well it is enforced, other drunk driving laws in effect, and public attitudes concerning alcohol; and (7) despite the absence of a strong causal link between .08 BAC laws by themselves and reductions in traffic fatalities, other evidence, including medical evidence on drivers' impairment, should be considered when evaluating the effectiveness of .08 BAC laws.