Marijuana and Driving

Driving Under the Influence of Cannabis

Driving is a complex task that requires integrity of sensory, motor, and cognitive function. The driving task may be compromised by factors related to the vehicle, the driving environment, and the driver. Driver impairment is a major cause of motor vehicle crashes and commonly results from alcohol intoxication. Cannabis is the most frequently detected illicit drug among drivers involved in motor vehicle crashes, often in combination with alcohol. Evidence from experimental and epidemiological studies indicates that cannabis also impairs driving performance and increases crash risk. The prevalence of cannabis use is expected to increase following recent legalization of medical and recreational use in several countries worldwide and the introduction of a legal cannabis industry. As a result, driving under the influence of cannabis has become an increasing public health concern.

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Marijuana-Impaired Driving Policy Statement

We Save Lives, DUID Victim Voices and High Means DUI, a project of SAM, Smart Approaches to Marijuana, joined forces to develop policies to combat marijuana-impaired driving. These policies are recommended for all states, regardless of the legal status of marijuana use. These policies neither condemn nor support marijuana legalization, but focus only on driving impairment by marijuana and other drugs.

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Washington Traffic Safety Commission

This report provides select updated fatal crash information originally presented in Washington Traffic Safety Commission’s report Driver Toxicology Testing and the Involvement of Marijuana in Fatal Crashes, 2010-20141 (October 2015). Since that report was published, poly-drug drivers involved in fatal crashes have increased significantly and is described more thoroughly in the present report.

The following is an excerpt of observations from the report:

  • Driver impairment due to alcohol and/or drugs is the number one contributing factor in Washington fatal crashes and is involved in nearly half of all traffic fatalities. Poly-drug drivers (combinations of alcohol and drugs or multiple drugs) is now the most common type of impairment among drivers in fatal crashes.
  • Among drivers in fatal crashes 2008-2016 that tested positive for alcohol or drugs, 44 percent tested positive for two or more substances (poly-drug drivers). The most common substance in poly-drug drivers is alcohol, followed by THC. Alcohol and THC combined is the most common poly-drug combination.
  • For the first time in 2012, poly-drug drivers became the most prevalent type of impaired drivers involved in fatal crashes. Since 2012, the number of poly-drug drivers involved in fatal crashes have increased an average of 15 percent every year.

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