Marijuana & Driving

  • Marijuana significantly impairs judgment, motor coordination, and reaction time, and studies have found a direct relationship between blood THC concentration and impaired driving ability.[1]
  • A study conducted at the University of Iowa’s National Advanced Driving Simulator found drivers who use alcohol and marijuana together weave more on a virtual roadway than drivers who use either substance independently.[2]
  • Marijuana is the illicit drug most frequently found in the blood of drivers who have been involved in a crash, including fatal ones (although it is important to note that marijuana can remain detectable in body fluids for days or even weeks after acute intoxication).[3]
  • A meta-analysis of multiple studies found that the risk of being involved in a crash roughly doubles after marijuana use.[4]
  • Crash-involved drivers with THC in their blood, particularly higher levels, are three to seven times more likely to be responsible for the crash than drivers who had not used drugs or alcohol. The risk associated with marijuana in combination with alcohol appears to be greater than that for either drug by itself.[5]

National Highway Traffic Safety Administration (NHTSA) 2013-2014 National Roadside Survey of Alcohol and Drug Use by Drivers showed that approximately 12.6 percent of drivers had evidence of marijuana use in their systems, up from 8.6 percent in 2007.[6]

NHTSA 2013-2014 National Roadside Survey of Alcohol and Drug Use by Drivers showed marijuana users were about 25 percent more likely to be involved in a crash than drivers with no evidence of marijuana use.[7]

Recent use of THC the risk of being killed in a fatal crash is similar to a driver with a BAC of up to approximately 0.151.[8]

Marijuana is now related to a record high of 33% of DUI cases in Washington state since it legalized recreational use.9

  1. Lenné M, Dietze P, Triggs T, Walmsley S, Murphy B, Redman J. The effects of cannabis and alcohol on simulated arterial driving: influences of driving experience and task demand. Accid Anal Prev. 2010;42:859-866. Hartman RL, Huestis MA. Cannabis effects on driving skills. Clin Chem. 2013;59:478-492.

Marilyn Heutis, et al., Cannabis Effects on Driving lateral Control with and Without Alcohol, 2015.
Brady JE, Li G. Trends in alcohol and other drugs detected in fatally injured drivers in the United States, 1999-2010. Am J Epidemiol. 2014;179(6):692-699.
Ramaekers JG, Berghaus G, van Laar M, Drummer OH. Dose related risk of motor vehicle crashes after cannabis use. Drug Alcohol Depend. 2004;73:109-119.
Hartman RL, Huestis MA. Cannabis effects on driving skills. Clin Chem. 2013;59:478-492.
www.nhtsa.gov
Id.
VicRoads. (n.d.) Cannabis & road safety.
Smart Approaches to Marijuana February 17, 2016 report.

[1] Lenné M, Dietze P, Triggs T, Walmsley S, Murphy B, Redman J. The effects of cannabis and alcohol on simulated arterial driving: influences of driving experience and task demand. Accid Anal Prev. 2010;42:859-866. Hartman RL, Huestis MA. Cannabis effects on driving skills. Clin Chem. 2013;59:478-492.
[2] Marilyn Heutis, et al., Cannabis Effects on Driving lateral Control with and Without Alcohol, 2015.
[3] Brady JE, Li G. Trends in alcohol and other drugs detected in fatally injured drivers in the United States, 1999-2010. Am J Epidemiol. 2014;179(6):692-699.
[4] Ramaekers JG, Berghaus G, van Laar M, Drummer OH. Dose related risk of motor vehicle crashes after cannabis use. Drug Alcohol Depend. 2004;73:109-119.
[5] Hartman RL, Huestis MA. Cannabis effects on driving skills. Clin Chem. 2013;59:478-492.
[6] www.nhtsa.gov
[7] Id.
[8] VicRoads. (n.d.) Cannabis & road safety.