More research is needed to better understand the relationship between cannabis use and road safety—particularly studies focused on developing and testing methods to precisely measure cannabis-induced driving impairment.
Studies have found a relationship between acute (short-term) cannabis intoxication and impaired driving ability.7–9,114 Cannabis is the illicit drug most frequently found in the blood of drivers involved in motor vehicle crashes, including fatal ones.10 A 2017 report from the National Academies Sciences, Engineering, and Medicine and several meta-analyses of multiple studies found that the risk of being involved in a crash increased after cannabis use.13,14–16,114 However, a study conducted by the National Highway Traffic Safety Administration found no significant increased crash risk attributable to cannabis use.17
Determining the precise role of cannabis use in motor vehicle crashes and impaired driving can be challenging for several reasons. Importantly, the drug may be detected in body fluids for days or even weeks after experiencing intoxication, and cannabis may affect driving ability differently among people who use it occasionally compared with those who use it regularly. Further, people often consume cannabis and alcohol together,8,118-120 and the risk for collisions associated with cannabis in combination with alcohol appears to be greater than that for either drug by itself.8
- For more information about drug-impaired driving, visit the National Highway Traffic Safety Administration.
- Learn more about cannabis and driving from the Centers for Disease Control and Prevention.