|DWI DETECTION GUIDE

Weaving plus any other cue: p = at least .65

Any two cues: p = at least .50



Problems Maintaining Proper Lane Position 
p=.50­.75

Weaving, Weaving across lane lines, Straddling a lane line, Swerving,
Turning with a wide radius, Drifting, Almost striking a vehicle or other
object

Speed and Braking Problems
p=.45­.70

Stopping problems (too far, too short, or too jerky), Accelerating or
decelerating for no apparent reason, Varying speed, Slow speed (10+ mph
under limit)

Vigilance Problems 
p=.55­.65

Driving in opposing lanes or wrong way on one-way, Slow response to traffic
signals, Slow or failure to resond to officer's signals, Stopping in lane
for no apparent reason, Driving without headlights at night*, Failure to
signal or signal inconsistent with action*

Judgment Problems 
p=.35­.90

Following too closely, Improper r unsafe lane change, Illegal or improper
turn (too fast, jerky, sharp, etc.), Driving on other than the designated
roadway, Stopping inappropriately in response to officer, Inappropriate
or unusual behavior (throwing, arguing, etc.), Appearing to be impaired

POST STOP CUES
p > .85

Difficulty with motor vehicle controlsDifficulty exiting the vehicleFumbling with driver's license or registrationRepeating questions or commentsSwaying, unsteady, or balance problemsLeaning on the vehicle or other objectSlurred speechSlow to respond to officer/officer must repeatProvides incorrect information, changes answersOdor of alcoholic beverage from the driverp > .50 when combined with any other cue:Driving without headlights at nightFailure to signal or signal inconsistent with actionThe probability of detecting DWI by random traffic enforcement stops
at night has been found to be about three percent (.03).

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