The following is a list of symptoms in descending order of probability that the person observed is driving while intoxicated. The list is based upon research conducted by the National Highway Traffic Administration:

1. Turning with a wide radius
2. Straddling center of lane marker
3. "Appearing to be drunk"
4. Almost striking object or vehicle
5. Weaving
6. Driving on other than designated highway
7. Swerving
8. Speed more than 10 mph below limit
9. Stopping without cause in traffic lane
10. Following too closely
11. Drifting
12. Tires on center or lane marker
13. Braking erratically
14. Driving into opposing or crossing traffic
15. Signaling inconsistent with driving actions
16. Slow response to traffic signals
17. Stopping inappropriately (other than in lane)
18. Turning abruptly or illegally
19. Accelerating or decelerating rapidly
20. Headlights off

Speeding, incidentally, is not a symptom of DWI; because of quicker judgment and reflexes, it may indicate sobriety.