You are 30 years old and not on DUI probation. You are driving your own car, which needs no commercial license and carries no passengers for hire. At what blood alcohol concentration (BAC) does it become illegal for you to drive?

Why

With those four situations ruled out, the line is 0.08%, the limit for a driver over 21 in an ordinary vehicle. The handbook lists five limits in all and every other one is lower, which is why guessing the number is risky: 0.01% if you are under 21, 0.01% at any age while you are on DUI probation, 0.04% if you are driving a vehicle that requires a commercial driver's license, and 0.04% if you are driving a passenger for hire. So the number that applies to you depends on your age, your license, your passengers and your record. And 0.08% is not a safe-until mark. The handbook says almost everyone feels the effects of alcohol at levels below the legal limit, and that how impaired you are can be enough on its own: an arrest and a DUI conviction are possible with no BAC reading at all.