Driving Patterns Associated With DUI

What causes certain drivers to get pulled over by DUI officers? What driving patterns make the police suspect a driver may be drunk?

The National Highway Transportation Safety Administration (NHTSA) has identified the 20 most common "driving symptoms" exhibited by drunk drivers. For each symptom, NHTSA offers a numeric probability that the driver displaying this symptom is under the influence.

When multiple symptoms are observed, NHTSA says to add 10% to the highest valued symptom. For example, if the person drives with his headlights off after dark, turns illegally and drives into opposing traffic, the probability he is DUI is 55%.

DUI Driving Symptoms:

• Turning with a wide radius…65%
• Straddling center or lane marker…65%
• Appearing to be drunk…60%
• Almost striking an object or vehicle…60%
• Weaving…60%
• Driving outside the designated roadway…55%
• Swerving…55%
• Slow speed (more than 10 mph below the speed limit)…50%
• Stopping in traffic (without a reason)…50%
• Drifting…50%
• Following too closely (tailgating)…45%
• Driving with tires on center or lane marker…45%
• Erratic braking…45%
• Driving into opposing traffic…45%
• Signaling inconsistently with driving actions…40%
• Stopping inappropriately (other than in lane)…35%
• Turning abruptly or illegally…35%
• Accelerating or decelerating suddenly…30%
• Headlights off after dark…30%

*Notice what is not on this list: Speeding. Many DUI cases begin with the driver getting pulled over for speeding. Many DUI officers claim that speeding is one of the factors suggesting the driver to be drunk. Yet the studies show no substantial correlation between DUI and driving in excess of the speed limit. A speeding driver is no more likely to be drunk than sober.