How do you know when you've had enough to drink? That can be a more difficult question than it seems at first. You may think you know when you've had enough. But do you? In California, it's illegal to operate a vehicle if any one of the following conditions is true:

• You are over 21 and have a blood alcohol concentration (BAC) of .08 or over.

• You are driving a commercial vehicle and have a BAC of .04 or over.

• You are under 21 and have a BAC of .01 or greater OR you have been drinking, period. If you are under 21, the reasoning goes, it's illegal for you to drink anyway. Therefore, it's doubly illegal for you to drink and drive, even if you didn't drink enough to become inebriated.

• You are "under the influence" of alcohol or any drug.

California has these laws in place to protect its citizens from the dangers posed by drunk driving. You definitely don't want to get caught on the wrong side of them! The only way to be completely safe is not to drink and drive at all.