As a Driver, What's Your Alcohol IQ?

What you might experience as a pleasant buzz could be intoxication in the eyes of the law.

For a 150-pound man of average build, four drinks in an hour can raise blood alcohol levels beyond legal driving limits. Keep in mind that it takes at least 1 ¼ hours for the body to metabolize the alcohol from each 12-ounce beer, each shot, or each 6-ounce glass of wine.

Effective in 2005, all 50 states set the blood alcohol concentration (BAC) limit at 0.08. What exactly does this number represent?

What Is BAC?

A BAC measurement represents the ratio of alcohol to blood expressed as milligrams of alcohol per 100 milliliters of blood. So, a BAC of 0.08 means that the body has a ratio of 8 drops of alcohol for every 10,000 drops of blood.

Even with a BAC below the legal limit, a driver can be impaired. Alcohol consumption affects concentration, balance, vision, judgment of distance, reaction time, and the fine motor coordination required for braking, steering, and safe lane changes.

You can be convicted of alcohol-impaired driving at a lower BAC if you show signs of impairment, such as: driving too fast or slow for conditions; swerving, weaving or crossing the center line; responding slowly to traffic signals; and night driving without headlights.

Every state has a zero tolerance policy when it comes to younger drivers. If you are under 21, you cannot legally operate a motor vehicle with detectable amounts of alcohol in your bloodstream.

Measuring BAC

While a blood or urine test determines a person's BAC, law enforcement typically uses a hand-held device that measures the concentration of alcohol in the air of the lungs. To calculate the level of alcohol in someone's system, a breathalyzer converts a standard ratio of blood alcohol to breath alcohol.

Most states and the District of Columbia allow an arresting officer to take the license of a driver who either fails or refuses to take a breath or blood alcohol test. In some states, this refusal is a criminal offense.

Consequences of Impaired Driving

States describe the offense of driving while impaired by alcohol using different terms. The most common are DWI (Driving While Intoxicated) and DUI (Driving Under the Influence). Each year, 1.5 million Americans are arrested for driving under the influence of alcohol or drugs.

Offenders face consequences that include DMV traffic points, fines, community service, loss of license, and jail time. In cases involving repeat offenders, judges have even ordered the sale of the vehicle driven by the offender.

In addition to these consequences, fighting a charge of drunken driving entails legal expenses and a conviction could triple your insurance rates.

Want More Information?

  • Your club can provide additional information and educational materials about drinking and driving.
  • Many clubs sponsor designated driver programs around holidays.
  • The AAA Foundation for Traffic Safety Web site ( gives you access to in-depth research on issues related to drinking and driving.