Alcohol and driving behaviors associated with alcohol level

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Correlation of Driving Behaviors With Alcohol Level

Accurately determining alcohol level based on driving behavior may be difficult. In one study, some behaviors typically associated with driving impairment were found in individuals well under the legal limit. [Burns. M., Dioquino, T., A Florida Validation Study of the Standardized Field Sobriety Test (SFST) Battery, 1997, p. 27 (hereafter "SFST FL Validation 1997").]

Average BAC Associated With Certain Driving Behaviors

Driving Behavior

Average BAC

Percentage

Equipment Violation

0.015%

10.2

Speed (high or low)

0.036%

28.6

Running Stop Sign/Failure to Yield etc.

0.038%

32.7

Drifting/Weaving

0.035%

20.4

Failure to Maintain a Single Lane

0.040%

8.2


In addition to this study, the National Highway Traffic Safety Administration, known as "NHTSA", provided a list of driving behaviors and their related probability of discriminating "nighttime drunk drivers" with sober drivers. Although the probability is numerically represented, the NHTSA list provides the number "primarily to emphasize the importance of a particular cue." The cues were determined to relate to drivers who may have a BAC of 0.10% or greater. [U.S. Department of Transportation, National Highway Traffic Safety Administration, Guide to Detecting Drunk Drivers at Night, DOT HS 805-711, 1982, pp 1-8.]

Driving Cues and Probability of .10% BAC

Cue

Probability

Turning with a wide radius: the distance between the turning vehicle and the center of the turn is greater than normal.

65

Straddling center or lane marker: vehicle is moving straight ahead with the center or lane marker between the left and right wheels.

65

Appearing to be drunk: eye fixation, tightly griping wheel, slouching in seat, erratic or obscene gestures, face close to windshield, drinking in the vehicle, driver's head protruding from the vehicle.

60

Almost striking object or vehicle: passing abnormally close to an object or vehicle, causing another vehicle to maneuver to avoid collision.

60

Weaving: moving from one side of the roadway to the other in a zig-zag course.

60

Driving on other than designated roadway: driving at the edge of roadway, on the shoulder, off the roadway, straight through turn-only lanes.

55

Swerving: an abrupt turn from a straight course.

55

Speed slower than 10 m.p.h. below limit

50

Stopping without cause in traffic lane; stopping without observable justification.

50

Following too closely; flowing another car without maintaining minimum legal separation.

50

Drifting: driving in a straight line but at an angle to the roadway.

50

Tires on center or lane marker; the left hand set of tires is "consistently" on the center line, or either set is "consistently" on the lane marker.

45

Braking Erratically; braking in an uneven/jerky manner, unnecessarily maintaining pressure on the brake peddle "riding the brakes."

45

Driving into opposing or crossing traffic: driving into opposing lane, backing into traffic, failing to yield the right of way, driving the wrong way on a one-way street.

45

Signaling inconsistent with actions: such as failing to signal a lane change, signaling opposite to the action, driving with hazard flashers etc.

40

Slow response to traffic signals: a longer than normal driver response to a change in the traffic signal.

40

Stopping inappropriately: vehicle stops at an inappropriate location or under inappropriate conditions other than in the traffic lane (flashing yellow light, green light, in a crosswalk etc.).

35

Turning abruptly or illegally: turning with excessive speed, turning sharply from the wrong lane, illegal U-turn, turning outside a designated turn lane.

35

Accelerating or decelerating rapidly: abrupt stop, breaking traction, acceleration or deceleration more rapid than required by traffic conditions.

30

Headlights off: driving with the headlights off at a time of day when headlights are required.

30