Legal Limit

It is illegal in every state to operate a motorized vehicle with a blood alcohol content (BAC), also called Blood Alcohol Concentration, which is 0.08% or higher. So any BAC lower than this allowable amount is considered a "legal limit." Consider also, commercial drivers have a lower legal limit to operate a motorized vehicle. Commercial drivers, who operate a commercial vehicle with a BAC of .04% or higher, can be charged with DUI.

Additionally, drivers under 21 years of age can be subject to zero tolerance laws which limit the amount of alcohol which can be present in their blood when they operate a motorized vehicle. This amount varies by state.

Drivers can, however, be arrested and convicted for drunk driving even if their BAC is under the legal limit if the state can prove their driving was impaired with a failed sobriety test, erratic driving, causing an accident or injury to another driver, etc.

The legal limit is simply the point the state has determined most drivers become too impaired to drive because they may become increasingly over confident, have difficulty remembering facts, have slurred speech, and trouble walking. If a driver's BAC is above the legal limit they can be automatically charged and convicted of DUI as long as the state has sufficient evidence such as a valid chemical test.