Driving Under the Influence of Alcohol and Marijuana: Beliefs and Behaviors, United States, 2013-2015

Thursday, February 2, 2017

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The purpose of this study was to provide estimates of the prevalence of self-reported use
and driving under the influence of alcohol and marijuana, and related perceptions and
beliefs among drivers 18 and older in the United States, and to present an analysis of
changes in these behaviors between 2013 and 2015. The data analyzed were collected via
nationally-representative surveys administered during this period.
From 2013-2015, an estimated 14.0 percent of drivers drove with a BAC close to or over the
legal limit in the past year, and 4.6 percent drove within an hour of using marijuana.
Drivers are divided with regard to their perceptions of the effect of using marijuana an hour
prior to driving on one’s risk of causing a crash: 58.3 percent believe this risk is increased,
6.2 percent believe it is not affected, 3.6 percent believe it is decreased, and 31.8 percent
indicated that they do not know how using marijuana an hour before driving affects crash
risk. Drivers who reported using marijuana, and those who reported driving within an hour
of use in the past year were less likely to believe that using marijuana increases crash risk,
and more likely to believe that such use does not affect or decreases crash risk. Awareness
of per se DUI laws for marijuana was low: in states that did have a per se law, only 48.5
percent were aware of it; in states without a per se law, 44.7 percent indicated incorrectly
that their state had such a law. Irrespective of whether their state actually had a per se law
for marijuana, more than half of all drivers reported that they did not know whether or not
their state had such a law.