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Status Report, Vol. 36, No. 6 | June 30, 2001 Subscribe

BAC limits of 0.08 percent are effective, studies show

A hot issue in state legislatures lately has been whether to lower the blood alcohol concentration (BAC) at or above which it's illegal to drive. Part of the debate is whether a 0.08 percent BAC threshold instead of 0.10 percent has any effect on crashes involving alcohol. A soon-to-be-released federal review concludes it does.

Many studies of 0.08 laws have been conducted. The new review by the Centers for Disease Control and Prevention's National Center for Injury Prevention and Control is one of the first to systematically analyze existing research. It includes several large multistate studies. On average, crash deaths involving alcohol dropped 7 percent after 0.08 percent BAC laws were adopted, says lead researcher Ruth Shults.

In some states, it's impossible to determine how much of the crash reductions are due to 0.08 laws or to the administrative license suspension (ALS) laws adopted about the same time. ALS laws, which allow license suspension immediately when a driver fails or refuses to take a BAC test, have been shown to deter alcohol-impaired driving (see "New laws to curb drinking drivers save many lives," March 14, 1988). Studies in states with long-standing ALS laws indicate an additional 5 to 8 percent crash reduction associated with 0.08 percent BAC thresholds.

Another question addressed by the review is whether 0.08 percent BAC laws deter alcohol-impaired driving at higher BACs. Five of the reviewed studies look at fatally injured drivers with BACs at or above 0.10 percent. Reductions in fatalities among these drivers were reported for most states.

More than half of the states have 0.08 percent BAC laws. Those that don't will lose a portion of their federal highway construction funds starting in October 2003.

BAC map of the U.S.

Forty-nine states and the District of Columbia have laws defining it as a crime to drive with a blood alcohol concentration (BAC) at or above a proscribed level — 0.08 percent in 27 states and the District of Columbia, 0.10 percent in 22 other states. In Massachusetts, a BAC of 0.08 percent is evidence of alcohol impairment, but it isn't illegal per se.

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