Why Was I Pulled Over? DUI, Probable Cause and Impaired Driving Clues

Here are some of the most common reasons law enforcement may suspect a driver is impaired.

The National Highway Traffic Safety Administration (NHTSA) has published a list of 24 visual "Cues" or indicators of drivers impaired by drugs or alcohol based on three field studies involving twelve thousand vehicle stops. Reproduced below are the 24 NHTSA cues, broken into four categories:

1) Difficulty Maintaining Proper Lane Position; 2) Speed and Braking Problems; 3) Vigilance Problems; and 4) Judgment Problems.

NHTSA's 24 Visual Cues Of Impaired Driving:

  • Weaving Within The Same Lane
  • Weaving Across Lane Lines
  • Straddling A Lane Line
  • Swerving
  • Turning With A Wide Radius
  • Drifting
  • Almost Striking A Vehicle Or Other Object
  • Problems Stopping Correctly
  • Accelerating Or Decelerating For No Apparent Reason
  • Varying Speed
  • Going Ten Or More Mph Below The Speed Limit
  • Driving On Wrong Side Of Road Or Wrong Way Down One Way Road
  • Slow To Respond To Traffic Signals, E.G. Traffic Light Change
  • Slow Or Failure To Respond To Officer'S Signals
  • Stopping In Lane For No Apparent Reason
  • Driving At Nights Without Headlights On
  • Failure To Signal Or Improper Signaling
  • Following Too Closely
  • Improper Lane Change/ Unsafe Lane Change
  • Improper Or Illegal Turn
  • Driving On Other Than The Designated Roadway
  • Stopping Inappropriately In Response To Officer
  • Inappropriate Or Unusual Behavior
  • Appearing Impaired

The NHTSA publication upon which this article is based is available for free download at: Visual Detection of DWI Motorists


Tennessee law enforcement officers are trained to look for the above-listed 24 visual cues when looking for impaired drivers. If you were stopped for suspicion of DUI or DWI and the basis of your stop did not include one of the above, you may have a basis for challenging the legality of your stop and any subsequent evidence police obtained from you, such as a blood or breath test. Challenging the legality of the stop is always the first step in fighting a DUI or DWI charge in Tennessee. Notice that speeding is not one of the 24 visual cues of impaired driving.

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