Science on Cannabis

Impaired Driving, Traffic Fatality Risk

To learn about what scientists are discovering about cannabis and the risk of traffic fatalities, click on the titles of the research studies below.


Researchers say nationwide marijuana legalization will add 6800 traffic fatalities annually.

Click for JAMA Study.

U.S. Research Studies

Use of Alcohol and Cannabis Among Adults Driving Children in Washington State

Romano 2019: Romano, E., Kelley-Baker, T, Eichelberger, A., Ramirez, A.

–Journal of Studies of Alcohol and Drugs

Recreational Cannabis Use Impairs Driving Performance in the Absence of Acute Intoxication

Dahlgren 2020: Dahlgren, K., Sagar, K.A., Smith, R.T., Lambros, A.M., Kuppe, M.K., Gruber, S.A.

–Drug and Alcohol Dependence

The Effect of Cannabis Compared with Alcohol on Driving

Sewell 2009: Sewell, A., Poling, J., Sofuoglu, M.

–American Journal on Addictions

Effects of Chronic Marijuana Use on Driving Performance

Doroudgar 2018: Doroudgar, S., Chuang, H.M., Bohnert, K., Canedo, J., Burrowes, S., Perry, P.J.

–Traffic Injury Prevention

Cannabis effects on driving lateral control with and without alcohol

Hartman 2015: Hartman, R.L., Brown, T.L., Milavetz, G., Spurgin, A., Pierce, R.S., Gorelick, D.A., Gaffney, G., Huestis, M.A.

–Drug and Alcohol Dependence

Cannabis Effects on Driving Skills

Hartman 2013: Hartman, R.L., Huestis, M.A.

–Clinical Chemistry, March 2013

Fatal crashes in the 5 years after recreational marijuana legalization in Colorado and Washington

Aydelotte 2019:  Aydelotte JD, Mardock AL, Mancheski CA et al.

–Accident Analysis & Prevention

The April 20 Cannabis Celebration and Fatal Traffic Crashes in the U.S.

Staples 2018: Staples, J.A., Redelmeier, D.A.

–JAMA Internal Medicine, April 2018

Drug Recognition Expert (DRE) examination characteristics of cannabis impairment

Hartman 2016: Hartman, R.L., Richman, J.E., Hayes, C.E., Huestis, M.A.

–Accident Analysis and Prevention

Marijuana and DUI Fatal Crashes Differ
by Time of Day & Day of Week

Crancer 2017: Alfred Crancer, B.S., M.A., Phillip Drum, Pharm. D.


Delays in DUI Blood Testing: Impact on Cannabis DUI   Assessments

Wood 2015: Ed Wood, Ashley Brooks-Russell, Phillip Drum, Pharm. D.


International Studies

Psychomotor Function in Chronic Daily Cannabis Smokers during Sustained Abstinence

Bosker 2013:  Bosker WM, Karschner EL, Lee D, Goodwin RS, Hirvonen J, et al.

–Clinical Trial

Cannabis and tolerance: acute drug impairment as a function of cannabis use history

Ramaekers 2016:  Ramaekers JG, van Wel JH, Spronk DB.

–Scientific Reports

Government Reports

Monitoring Health Concerns Related to Marijuana in Colorado: 2016

See Marijuana Use and Driving section pg 145-156

Driving Under the Influence of Drugs and Alcohol

A Report Pursuant to U.S. House Bill 17-1315

Position on Cannabis (Marijuana) and Driving

2017, NSC Alcohol, Drugs and Impairment Division

–National Safety Council

Marijuana Use, Alcohol Use, and Driving in Washington State

Grondel 2018: Grondel D, Hoff S, Doane D.  

–Washington State Traffic Safety Commission