The Visual Detection of DWI Motorists

Summary

To summarize, the DWI cues related to problems in maintaining proper lane position include,

  • Weaving,
  • Weaving across lane lines,
  • Straddling a lane line,
  • Drifting,
  • Swerving,
  • Almost striking a vehicle or other object, and
  • Turning with a wide radius, or drifting during a curve.

The DWI cues related to speed and braking problems include,

  • Stopping problems (too far, too short, too jerky),
  • Accelerating for no reason,
  • Varying speed, and
  • Slow speed.

The DWI cues related to vigilance problems include,

  • Driving without headlights at night,
  • Failure to signal a turn or lane change, or Signaling inconsistently with actions,
  • Driving in opposing lanes or the wrong way on a one-way street,
  • Slow response to traffic signals,
  • Slow or failure to repsond to officer's signals, and
  • Stopping in the lane for no apparent reason.

The DWI cues related to judgment problems include

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

Post-Stop Cues

In addition to the driving cues, the following post-stop cues have been found to be excellent predictors of DWI.

  • Difficulty with motor vehicle controls,
  • Difficulty exiting the vehicle,
  • Fumbling with driver's license or registration,
  • Repeating questions or comments,
  • Swaying, unsteady, or balance problems,
  • Leaning on the vehicle or other object,
  • Slurred speech,
  • Slow to respond to officer/officer must repeat questions,
  • Provides incorrect information or changes answers, and
  • Odor of alcoholic beverage from the driver.

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