Approximately what blood alcohol concentration is the common legal limit for driving for adults in most U.S. states?

In most U.S. states, the common legal limit for driving for adults age 21 and over is a blood alcohol concentration of 0.08%. (Lower limits often apply to commercial drivers and to drivers under 21, who are typically subject to 'zero tolerance' laws.) At 0.08% BAC, a person's coordination, reaction time, and judgment are significantly impaired. Servers do not measure BAC, but knowing the legal driving limit reinforces why preventing intoxicated customers from driving — and avoiding over-service — is so important for public safety and liability.