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|Contents

The DWI Detection Guide

Explanations of the 24 driving cues

Summary

A description of post-stop cues that
are predictive of DWI
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|Introduction

More than a million people have died in traffic crashes in the United
States since 1966, the year of the National Traffic and Motor Vehicle Safety
Act, which led to the creation of the National Highway Traffic Safety Administration,
or NHTSA.

During the late 1960s and early 1970s more than 50,000 people lost their
lives each year on our nation's streets, roads and highways. Traffic safety
has improved considerably since that time: the annual death toll has declined
substantially, even though the numbers of drivers, vehicles, and miles driven
all have increased. When miles traveled are considered, the likelihood of
being killed in traffic during the 1960s was three to four times what it
is today.

The proportion of all crashes in which alcohol is involved also has declined.
The declines in crash risk and the numbers of alcohol-involved crashes are
attributable to several factors, including the effectiveness of public information
and education programs, traffic safety legislation, a general aging of the
population, and law enforcement effort.

NHTSA research contributed to the improved condition, in part, by providing
patrol officers with useful and scientifically valid information concerning
the behaviors that are most predictive of impairment. Continued enforcement
of DWI laws will be a key to saving lives in the future. For this reason,
NHTSA sponsored research leading to the development of a new DWI detection
guide and training materials, including a new training video. Many things
have changed since 1979, but like the original training materials, the new
detection guide describes a set of behaviors that can be used by officers
to detect motorists who are likely to be driving while impaired.

Building upon the previous NHTSA study, the researchers interviewed officers
from across the United States and developed a list of more than 100 driving
cues that have been found to predict blood alcohol concentrations, or BACs,
of 0.08 percent or greater. The list was reduced to 24 cues during three
field studies involving hundreds of officers and more than 12,000 enforcement
stops. The driving behaviors identified by the officers are presented in
the following four categories:

1) Problems in maintaining proper lane position,
  2 ) Speed and braking problems,
  3) Vigilance problems, and
  4) Judgment problems.

The cues presented in these categories predict that a driver is DWI at
least 35 percent of the time. For example, if you observe a driver to be
weaving or weaving across lane lines, the probability of DWI is more than
.50, or 50 percent. However, if you observe either of the weaving cues and
any other cue listed in this booklet, the probability of DWI jumps to at
least .65, or 65 percent. Observing any two cues other than weaving indicates
a probability of DWI of at least 50 percent, although some cues, such as
swerving, accelerating for no reason, and driving on other than the designated
roadway, have single-cue probabilities greater than 70 percent. Generally,
the probability of DWI increases substantially when a driver exhibits more
than one of the cues.

The research suggests that these training materials will be helpful to
officers in:

Detecting impaired motorists,Articulating observed behaviors on arrest reports, andSupporting officers' expert testimony.Back to Top
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