DUI DRIVING SYMPTOMS
Usually, the first thing that attracts a police officer's attention in a drunk driving case is the individual's driving. Nevada police officers are trained what driving symptoms to be looking for. And many of them have been trained with the aid of a booklet published by the federal government (National Highway Traffic Safety Administration). The booklet, entitled Guide for Detecting Drunk Drivers at Night: A DUI Detection Guide, is based upon federally-financed field research and identifies the nineteen most common and reliable initial indicators of drunk driving.
The list of symptoms which follow include the probability that the driver is intoxicated. For example, the research indicates that the chances are 65 out of 100 that a driver who is straddling a center or lane marker has a blood-alcohol concentration of .10 percent or higher (the research was conducted before blood-alcohol levels were dropped to .08 percent).
- Turning with Wide Radius 65
- Straddling Center or Lane Maker 65
- Appearing to be Drunk 60
- Almost Striking Object or Vehicle 60
- Weaving 60
- Driving on Other Than Designated Roadway 55
- Swerving 55
- Slow Speed (more than 10 mph below limit) 50
- Stopping (without cause) in Traffic Lane 50
- Drifting 50
- Following Too Closely 45
- Tires on Center or Lane Maker 45
- Braking Erratically 45
- Driving Into Opposing or Crossing Traffic 45
- Signaling Inconsistent with Driving Actions 40
- Stopping Inappropriately (other than in lane) 35
- Turning Abruptly or Illegally 35
- Accelerating or Decelerating Rapidly 30
- Headlights Off 30
It may come as a surprise to many that, for example, 40 out of 100 drivers "appearing to be drunk" to police officers are, in fact, not under the influence. Similarly, 40 out of 100 drivers who are weaving or who almost strike another vehicle are also legally sober.
The research indicates that the chances of a driver being intoxicated when multiple symptoms are observed can also be calculated: "When two or more cues are seen, add 10 to the highest value among the cues observed." For example, if the subject is observed to be straddling a lane marker (60) and breaking erratically (45), there are 70 chances out of 100 that he has a blood-alcohol concentration of .10 percent or more. Of course, this also means that 30 out of 100 drivers who are straddling and breaking erratically are NOT under the influence.