The legal blood alcohol concentration (BAC) limit is 0.08 in the United States. Several states have a lower limit, however, so the actual legal limit may vary from state to state. There are also some other factors affecting how much alcohol you can have in your system. For example, your body weight and physical traits affect how much alcohol is metabolized by your system. In addition, the food you eat and your overall health affect how much alcohol your body can process.
Despite the fact that a person’s BAC level is often a factor in determining if they are impaired and if they will be arrested for drunk driving, 0.08% BAC laws have not been proven to decrease the rate of alcohol-related traffic crashes. However, research has shown that they do not lead to a higher rate of injury and death. These laws save lives in combination with other drunk driving legislation and enforcement, and further research is necessary to determine their effectiveness.
Researchers at the National Highway Traffic Safety Administration have studied the impact of California’s 0.08% BAC law. In particular, they have examined the effects of the law on driver’s alcohol involvement. Previously, there had been no law restricting a motorist’s ability to drive with a BAC below 0.05. During this time, the rate of alcohol-related traffic fatalities declined by 7 percent.
A few states, including New Mexico and Illinois, had lower criminal per se legal limits of 0.10%. When the 0.08% BAC law was implemented, these states adopted new levels of legal limits. According to the Association for the Advancement of Automotive Medicine, this change in policy accounted for more than one-quarter of the reduction in alcohol-related traffic deaths in the U.S. Across the nation, alcohol-related crashes claimed nearly 17,000 lives in 1998.
Among those affected by the law are drivers of commercial motor vehicles and people under age 21. In general, those under 21 are subject to the same regulations as adults, and any detectable amount of blood alcohol in their system is a violation. Some of the consequences of having a BAC above 0.08% include loss of judgment, distraction, and diminished coordination.
In fact, a woman who weighs 120 pounds can reach a BAC of 0.08% after only two drinks within an hour. Most men would need to consume at least three drinks to reach the same level. Similarly, a heavy drinker, such as a man who weighs 180 pounds, can achieve a BAC of 0.08% after just four drinks.
Compared with states that have not enacted a 0.08% BAC law, those that do see a 6% decrease in blood alcohol levels post-law. This is not a large reduction, but in general, a 0.08% BAC law can help reduce the number of drunk-driving related traffic crashes in the U.S. In some cases, a 0.08% BAC law has led to a significant decrease in alcohol-related traffic deaths.
Currently, ten states do not have a 0.08% BAC law in place. Nevertheless, a study by the General Accounting Office showed that there was not a large impact on alcohol-related traffic deaths in these states. It also did not assess the relationship between a 0.08% BAC law and regional trends.