How does alcohol affect a driver's ability to operate a vehicle safely?

Alcohol is a depressant that impairs the very abilities driving requires: judgment, reaction time, coordination, concentration, and vision. These effects begin even at low blood alcohol concentrations, before a driver reaches the legal limit, and they worsen as more alcohol is consumed. Impaired drivers misjudge speed and distance, react slowly, and take greater risks. The only safe choice is not to drive after drinking — use a designated driver, a rideshare, or wait. Many other substances, including certain medications and drugs, also impair driving. Understanding alcohol's effects underlies impaired-driving laws and is heavily tested.