The Detection of DWI Motorcyclists
A Resource for Law Enforcement Personnel
Introduction
There are approximately eight and a half million street-legal motorcycles registered in the United States. Each year, one out of every 35 of those motorcycles is involved in a reported crash, and one out of every 1,200 or so is involved in a fatal crash.
When fatalities per miles traveled are considered, motorcyclists are killed at about 19 times the rate of drivers and passengers of other motor vehicles. The National Highway Traffic Safety Administration (NHTSA) data shows that in 2003, 41 percent of motorcycle rider (and passenger) fatalities involved alcohol.
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In Minnesota in 2006, 70 people were killed in motorcycle crashes. Of the 61 motorcycle operators tested in these fatal crashes, 19 (31 percent) tested positive for alcohol use--18 of these riders were over the legal limit of .08 BAC.
Objectives
The purpose of this Web page is to:
- Explain the problem of impaired riding, how it is different from impaired driving, and why it is important.
- Give peace officers 14 behavioral clues to help identify impaired (DWI) motorcyclists.
- Help peace officers articulate observed behaviors on arrest reports and when providing expert testimony.
Background
NHTSA sponsored the research necessary to develop a set of behavioral cues that can be used by law enforcement personnel to accurately detect motorcyclists who are operating their vehicles while intoxicated. The researchers began by interviewing expert patrol officers from across the country to determine what behavioral cues have been used to detect impaired motorcyclists. Most officers recalled at least a few cues that they use to discriminate between DWI and normal riding. A few, primarily motorcycle officers, suggested cues that reflected considerable understanding of the mental and physical requirements of riding a motorcycle. Others believe the cues to be identical to those used to detect impaired drivers. But some officers, even those with many years experience, reported that they believe there to be no cues that can be used to distinguish DWI from unimpaired motorcycle operation.
In addition to interviewing law enforcement personnel, the research team developed a data base of 1,000 motorcycle DWI arrest reports. They focused on the officers' narratives and the behaviors that motivated the stops, and correlated those behaviors with blood alcohol concentrations (BACs). Analysis of the interviews and arrest report data resulted in an inventory of about 100 cues that have been observed by officers in association with impaired motorcycle operation.
The researchers, working closely with the law enforcement personnel, conducted two major field studies involving more than 50 sites throughout the United States. Officers recorded information about every enforcement stop they made of a motorcyclist. Those field studies permitted the researchers to identify the most effective cues and to calculate the probabilities that those cues are predictive of DWI. This Web page presents the results of the research.
Fourteen cues were identified that best discriminate between DWI and unimpaired operation of a motorcycle. The cues have been
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labeled as "excellent predictors" and "good predictors" based on study results. The excellent cues predicted impaired motorcycle operation 50 percent or more of the time. The good cues predicted impaired motorcycle operation 30-49 percent of the time. The special coordination and balance requirements of riding a two-wheeled vehicle provided most of the behaviors in the excellent category of cues.
Table of Contents
The Motorcycle Rider
Excellent Cues (50+ percent probability)
Good Cues (30-49 percent probability)
Poor Cues (10 percent or less probability)
Skill Impairment at .03 and Greater BAC
(To order Detection of DWI Motorcylists video or brochures from the NHTSA Web site, click here.)
Last Updated 6/2/2008
