​It is illegal in Wisconsin for a driver over the age of 21 to operate a motor vehicle: With a Blood/Breath Alcohol Concentration (BAC) of 0.08 or greater; While under the influence of an intoxicant; With a detectable amount of a restricted controlled substance in his or her blood; or While under the influence of a controlled substance or any other drug.​ For drivers with three or more prior Operating While Intoxicated (OWI) convictions, the limit is lower; they cannot operate a motor vehicle if their BAC is greater than 0.02 Drivers under 21 years of age are required by law to maintain absolute sobriety and, for them, driving with any amount of alcohol in their system is illegal. Definitions A driver is under the influence when his or her ability to operate a motor vehicle is impaired. A person's ability to operate a motor vehicle is impaired if he or she is less able to safely control the vehicle because of the consumption of alcohol or controlled substances. This means that if a police officer pulls you over and determines that you are impaired by alcohol and/or any other drug, you could be arrested and prosecuted, regardless of your BAC. Penalties for operating a motor vehicle while intoxicated range from a forfeiture and license revocation for a first offense, to up to six years imprisonment and a lifetime license revocation for subsequent offenses. Additionally, more severe penalties apply if injury or death results. But no matter what your legal status, it is always wise to avoid driving if you have been drinking. A recent review of alcohol impairment studies by the National Highway Traffic Safety Administration (NHTSA) concluded that impairment of some driving-related skills begins with even the smallest amount of alcohol in your system.