What is the legal BAC limit for drivers over the age of 21?

The legal Blood Alcohol Concentration (BAC) limit for drivers over the age of 21 is 0.08%. This threshold is used to determine impaired driving and is recognized across many jurisdictions as a standard limit. Testing at this level or higher indicates that a person's ability to operate a vehicle is significantly affected by alcohol, resulting in impaired judgment, coordination, and reaction times.

The selection of 0.08% as the legal limit is based on extensive research that demonstrates impairments in driving performance at this BAC level. It strikes a balance between allowing responsible alcohol consumption and ensuring road safety by reducing the risk of accidents due to impaired driving.

In discussing the other options, it's important to note that 0.10% is considered above the standard legal limit for many places, indicating a higher level of impairment. Similarly, 0.06% and 0.04% are both below the legal limit for individuals over 21, which may apply to specific circumstances, such as commercial drivers or underage drivers, but they do not represent the standard legal threshold for general drivers.