It is illegal to drive if your Blood Alcohol Concentration (BAC) is...

• A. .08 or greater
• B. .10 or greater
• C. .05 or greater
• D. .00

Answer: (A)

A driver’s legal limit is set because alcohol impairs the abilities needed to operate a vehicle. The widely used per se limit is 0.08% BAC; at or above this level, reaction time slows, coordination suffers, and judgment is impaired, making driving legally unsafe and unlawful in many places. That’s why 0.08% BAC is the threshold you should know.

0.10% is simply a higher level of impairment and would also be illegal, but the standard threshold most often tested is 0.08%. A BAC of 0.05% is below the common legal limit in many jurisdictions (though impairment can occur earlier for some people), so it isn’t the typical cutoff. A BAC of 0.00% means no alcohol is in the blood, which is legal to drive.