DUIs: What Are the Visual Cues?

Why does a police officer decide to pull you over?

Have you ever wondered why a police officer decides to pull someone over for a DUI?

National Highway Traffic Safety Administration (NHTSA) researchers developed a list of more than 100 driving cues that have been found to predict blood alcohol concentrations (BAC) of 0.08 percent or greater. The list was reduced to 24 cues and these cues fall into four categories:

1) Problems in maintaining proper lane position

2) Speed and braking problems

3) Vigilance problems

4) Judgment problems

The cues presented in these categories can help predict whether a driver is DUI. For example, if an officer observes a driver to be weaving or weaving across lane lines, the probability of DUI is more than .50 or 50 percent. However, if an officer observes either of those weaving cues and any other cue listed below, the probability of DUI jumps to at least .65 or 65 percent.

Maintaining Proper Lane Position

This is the big giveaway for a DUI. Impaired drivers have an extremely difficult time maintaining proper lane position, most commonly witnesses as weaving. Weaving is when the vehicle alternately moves toward one side of the lane and then the other. The pattern of lateral movement can be fairly regular, as one steering correction is closely followed by another. In extreme cases, the vehicle’s wheels even cross the lane lines before a correction is made. An officer might even observe a vehicle straddling a center or lane line. That is, the vehicle is moving straight ahead with either the right or left tires on the wrong side of the lane line or markers. Drifting, another powerful cue, is when a vehicle is moving in a generally straight line, but at a slight angle to the lane. Indicators of failing to maintain proper lane position include:

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

Speed And Braking Problems

Braking properly can be a difficult task for an impaired driver. For example, there is a good chance the driver is DWI if an officer observes any type of stopping problem. Stopping cues include:

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

Vigilance Problems

Vigilance concerns a person’s ability to pay attention to a task or notice changes in surroundings. A driver whose vigilance has been impaired by alcohol might forget to turn on his or her headlights when required. Similarly, impaired drivers often forget to signal a turn or lane change, or their signal is inconsistent with their maneuver, for example, signaling left but turning right. Alcohol-impaired vigilance also results in motorists driving into opposing or crossing traffic and turning in front of oncoming vehicles with insufficient headway. Cues 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 respond to officer’s signals
  • Stopping in the lane for no apparent reason

Judgment Problems

Operating a motor vehicle requires continuous decision making by the driver. Unfortunately, judgment abilities can be affected by even small amounts of alcohol. For example, alcohol- impaired judgment can cause a driver to follow another vehicle too closely, providing an unsafe stopping distance. Alcohol-impaired judgment also can result in a driver taking risks or endangering others. Cues 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
  • 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 DUI.

  • 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 or officer must repeat questions
  • Providing incorrect information or changes answers
  • Odor of alcoholic beverage from the driver
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