If you think driving drunk is no big deal, think again. In the United States, federal law prohibits any person from operating a vehicle if he or she is under the influence of alcohol or drugs. In addition, each state has its own guidelines specifying just what constitutes driving while impaired (DWI) from a legal perspective—and like most states, Virginia’s DWI laws are strongly tied to blood alcohol concentration, or BAC.
BAC: What it means to you
Anytime you consume an alcoholic beverage—be it beer, wine, or hard liquor—alcohol must enter your bloodstream in order for your body to process it. The percentage of alcohol in your bloodstream, in turn, is known as your BAC.
Research suggests that a person’s ability to operate a vehicle becomes significantly impaired once the amount of alcohol in his or her system reaches 0.08% or higher. Based on this information, it is against the law for anyone to drive with a BAC above this amount. Under Virginia’s BAC guidelines, there are two exceptions to this rule: if you are under 21, you can be arrested for driving with a BAC of 0.02% or more; and if you operate a commercial vehicle, you must adhere to a 0.04% limit.
It is important to know that, because of these BAC limits, a person can be considered legally impaired even if he or she shows no signs of intoxication. Simply driving with an illegal BAC is enough to warrant an arrest for driving while impaired. However, if you do show signs of impairment (such as driving recklessly, for example), you could still be arrested—even if your blood alcohol concentration is within the legal limits.
Unfortunately, there’s no easy way for a driver to determine his or her BAC. Law enforcement officers must rely on professional testing equipment, such as breathalyzers and blood or urine tests, to measure a person’s blood alcohol concentration. If the test indicates you have a BAC above the legal limit, you can expect to be arrested and charged with DWI.