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How Law Enforcement Detects Impaired Motorists


The National Highway Traffic Safety Administration (NHTSA) conducted a study involving interviews by law enforcement authorities and extensive research to create a list of visual cues for detecting motorists who are under the influence of alcohol. These visual cues consist of four main categories of driving behavior, which officers use to determine whether to pull someone over on suspicion of DUI.

The following are the four major categories for drunk driving behavior:

  • Acceleration and braking problems – Drunk drivers often have a hard time driving at a consistent speed. Common indicators of speed issues include driving well over the posted speed limit and suddenly accelerating or decelerating for no valid reason. Common examples of braking issues include stopping either well before or beyond an intersection, making short and jerky stops, or stopping at odd angles.
  • Judgment difficulties – While you are operating a vehicle, you must constantly make judgments to protect yourself from breaking the law and injuries. Drunk drivers often lack alertness, making them more prone to take risks. Judgment problems include making unsafe lane changes and illegal turns, tailgating, and driving outside the roadways.
  • Difficulties staying in a driving lane – Impaired drivers experience problems maintaining adequate lane position. Common examples of this type of driving behavior include swerving, weaving, drifting toward one side of the roadway, and making extremely wide turns.
  • Awareness issues – Drunk drivers also fail to notice traffic signals, the flow of traffic, and other traffic conditions. Motorists who lack vigilance and awareness typically have delayed responses to traffic signals, drive in the dark without using their headlights, and even drive the wrong way.

When law enforcement notices one or more of these driving behaviors, it is enough to establish “reasonable suspicion” to make a lawful traffic stop. When the police officer approaches the vehicle, there are several signs which indicate intoxication, such as an alcohol odor, poor motor skills, slurred speech, slow responses to questions, and evidence of an open container in the vehicle.

If you have been charged with a DUI in Santa Barbara, contact our experienced legal team at Appel & Morse today.

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