Listed below are clues suggested by the National Highway Traffic Safety Administration as ways to distinguish between nighttime drunk and sober drivers.

~Turning with a wide radius.
~Straddling the center of the road or lane marker.
~Appearing to be drunk (i.e., eye fixation, face close to windshield, drinking in the vehicle).
~Almost striking an object or other vehicle.
~Weaving or zigzagging across the road.
~Driving on other than a designated roadway.
~Swerving or abruptly turning away from a generally straight course.
~Turning abruptly or illegally.
~Driving slower than 10 mph below speed limit.
~Stopping without cause in a traffic lane.
~Stopping inappropriately (other than in lane).
~Following others too closely.
~Drifting or moving in a straight-line at a slight angle to the roadway.
~Erratic braking.
~Driving into opposing or crossing traffic.
~Signaling that is inconsistent with driving actions.
~Slow response to traffic signals (sudden stop, delayed start).
~Driving with headlights off.