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According to the research performed for the National Highway Traffic Safety Administration, the following are some of the actions that may be indicators of driving while impaired:

  • Turning with a wide radius;
  • Straddling the center of the lane marker;
  • Appearing to be drunk;
  • Almost striking an object or vehicle;
  • Weaving;
  • Driving on anything other than the designated highway;
  • Swerving;
  • Speed more than 10 miles per hour below the speed limit;
  • Stopping without cause in the traffic lane;
  • Following too closely;
  • Drifting;
  • Tire on center or lane marker;
  • Braking erratically;
  • Driving into opposing or crossing traffic;
  • Signaling inconsistent with driving actions;
  • Slow response to traffic signals;
  • Stopping inappropriately (other than in lane);
  • Turning abruptly or illegally;
  • Accelerating or decelerating rapidly;
  • Headlights off;

It is worth noting that speeding is not generally considered to be a sign of driving while impaired.