In its brochure The Visual Detection of DWI Motorists, the National Highway Traffic Safety Administration (NHTSA) lays out 24 cues that police officers are instructed to look for in determining whether a driver might be intoxicated.
Those 24 cues are:
- Weaving (within a lane),
- Weaving across lane lines,
- Straddling a lane line,
- Turning with a wide radius,
- Almost striking a vehicle or other object,
- Stopping problems,
- Accelerating or decelerating for no apparent reason,
- Varying speed,
- Slow speed (10+ mph under the speed limit),
- Driving the wrong way on a one-way street,
- Slow response to traffic signals,
- Slow response/failure to respond to officer's signals,
- Stopping in lane for no apparent reason,
- Driving without headlights at night,
- Failure to signal,
- Following too closely,
- Unsafe lane change,
- Illegal turn,
- Driving off the road,
- Stopping inappropriately in response to officer,
- Inappropriate or unusual behavior, and
- Appearing to be impaired.
In my experience, most drivers are stopped either because they're speeding, have a broken headlight or taillight or they didn't signal a lane change.
Speeding, as the officer will have to concede, is not recognized as a common or reliable initial indicator of impairment. Likewise, an equipment violation has nothing to do with whether or not a motorist is intoxicated. The same goes for failure to signal lane changes; that traffic law is observed far more in the breach than in the observance.
But what do they all have in common? They are all traffic code violations, and according to Texas courts, it doesn't matter why the officer stopped you, as long as he had reason to believe that you violated a provision of the traffic code.