Blood Alcohol Concentration (BAC) refers to the percent of alcohol (ethyl alcohol or ethanol) in a person’s bloodstream and is usually determined by a breathalyzer test or a blood test when the police suspect a driver of being intoxicated. For example, a BAC of .10% means that the person’s blood supply contains one part alcohol for every 1,000 parts blood.

In most states a driver is considered legally intoxicated if their BAC is .08 or higher. This BAC level is generally prescribed by a state statute (a law enacted by the state legislature) and creates a presumption of intoxication—also known as per se BAC because it is intoxication by definition. In Utah, the per se BAC level is .05.

Most states have a zero-tolerance BAC level of .02 for drivers under the legal drinking age (usually 21) that will result in a DUI/DWI charge. And most states also have an enhanced penalty or aggravated DUI/DWI charge for drivers whose BAC is .15 or higher—with a few states placing this aggravated or enhanced-penalty DUI/DWI BAC level at .16 to .20.

In Rhode Island, the legal limit for Blood Alcohol Concentration (BAC) for drivers aged 21 and over is .08%, in line with the majority of states. This means that a driver with a BAC of .08% or higher is considered legally intoxicated and can be charged with Driving Under the Influence (DUI). For drivers under the age of 21, Rhode Island enforces a zero-tolerance policy, where any BAC above .02% can result in a DUI charge. The state also has enhanced penalties for high BAC levels; a driver with a BAC of .15% or higher may face more severe consequences under Rhode Island's DUI laws. These regulations are designed to discourage driving under the influence and to promote road safety.