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Signs police use to identify impaired drivers

On Behalf of | Jun 10, 2025 | DUI Defense

One key thing to note about impaired driving stops is that the police need a reason for the stop. They need to know that the driver is impaired in advance, or they need another reason to pull over the vehicle.

For instance, there are some cases in which police officers will simply see signs of impairment and pull a driver over to administer field sobriety tests or breath tests. There are other situations in which the officer will watch the vehicle commit a moving violation, like running a stop sign, and pull them over for that reason. After talking to the driver, the officer may smell alcohol or notice clear signs like slurred speech and bloodshot eyes—and it then becomes an impaired driving stop.

Common signs of impairment

If there isn’t another moving violation, here are some signs that a police officer may use to determine that someone is impaired, leading them to initiate a traffic stop:

  • Drifting back and forth in the traffic lane
  • Driving very far below the speed limit
  • Aggressively speeding
  • Drifting off the road and onto the shoulder or straddling the centerline
  • Not responding appropriately to green lights, red lights or other types of traffic signals
  • Driving carelessly and almost getting into accidents
  • Failing to turn on headlights at night
  • Not driving appropriately for conditions

It is important to understand these signs because an illegal stop—without reasonable suspicion—could be a violation of your rights. This can be very important if you’re facing drunk driving charges, so be sure you understand all of the defense options at your disposal.