The Real Effects

Alcohol steadily decreases a person’s ability to drive a motor vehicle safely. The more you drink, the greater the effect. Just like blood alcohol levels, the signs of impairment differ with the individual.

In single-vehicle crashes, the relative risk of a driver with BAC between .08 and .10 is at least 11 times greater than for drivers with a BAC of zero, and 52 times greater for young males. Further, many studies have shown that even small amounts of alcohol can impair a person’s ability to drive.

Every State has passed a law making it illegal to drive with a BAC of .08 or higher. A driver also can be arrested with a BAC below .08 when a law enforcement officer has probable cause, based on the driver’s behavior.

The following chart contains some of the more common symptoms people exhibit at various BAC levels, and the probable effects on driving ability:


Typical Effects

Predictable effects on driving


•Some losst of Judgment
•Body warmth
•Altered mood

•Decline in visual functions (rapid tracking of a moving target)
•Decline in ability to perform two tasks at the same time (divided attention)


•Exaggerated behavior
•May have loss of small-muscle control (e.g., focusing your eyes)
•Impaired judgment
•Usually good feeling Lowered alertness •Release of inhibition

•Reduced coordination
•Reduced ability to track moving objects
•Difficulty steering
•Reduced response to emergency driving situations


•Muscle coordination becomes poor (e.g., balance, speech, vision, reaction time, and hearing)
•Harder to detect danger
•Judgment, self-control, reasoning, and memory are impaired

•Short-term memory loss
•Speed control
•Reduced information processing capability (e.g., signal detection, visual search)
•Impaired perception


•Clear deterioration of reaction time and control
•Slurred speech, poor coordination, and slowed thinking

•Reduced ability to maintain lane position and brake appropriately


•Far less muscle control than normal
•Vomiting may occur (unless this level is reached slowly or a person has developed a tolerance for alcohol)
•Major loss of balance

•Substantial impairment in vehicle control, attention to driving task, and in necessary visual and auditory information processing

1 Information in this table shows the BAC level at which the effect usually is first observed, and has been gathered from a variety of sources including the National Highway Traffic Safety Administration, the National Institute on Alcohol Abuse and Alcoholism, the American Medical Association, the National Commission Against Drunk Driving, and


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Drink as a group, be responsible as a group

When you're out with friends, you're not just responsible for yourself. If you suspect that anyone in your group is impaired, join together to keep that person from driving.