The number of Washington state drivers involved in fatal crashes that tested positive for THC — the principal psychoactive ingredient in cannabis — has more than doubled since the state legalized recreational marijuana use in December 2012, a recent study showed.
Between 2013 and 2017, research by the AAA Foundation for Traffic Safety found that 18% of the drivers involved in fatal crashes on Washington state roadways tested positive for THC, a release on the study stated. That converts to approximately 130 drivers per year that tested positive..
From 2008 to 2012 — the five year period before recreational use was legalized — only 8.8% tested positive, or approximately 56 drivers per year, according to the study.
Those numbers are consistent with the number of THC-positive drivers the Washington State Traffic Safety Commission has seen, Region 11 Target Zero Manager Doug Dahl told The Bellingham Herald in an email.
“It confirms what we already knew: cannabis use negatively affects driving,” Dahl wrote.
Dahl wrote that though the AAA report’s findings on the increased number of THC-related fatal crashes is alarming, other studies have shown a 0.08 blood-alcohol level increases crash risks fourfold or more.
“Even more concerning … in many of our THC-positive fatal crashes the driver is also positive for alcohol, and that crash risk is much higher than the risk of impairment of a single substance — as high as 17 times more likely,” Dahl wrote. “Impairment is the No. 1 cause of fatal crashes in Washington, and poly-drug use is now the most prevalent form of impairment.”
Dahl cited a traffic safety commission study that found by 2016 the number of poly-drug drivers was more than double the number of alcohol-only drivers and five times more than the number of THC-only drivers involved in fatal crashes.
Though many of other factors were involved, Washington averaged 477.2 fatal crashes statewide between 2013 and 2017, according to statistics compiled from the Washington State Department of Transportation Crash Data Portal — up from the 417.3 the state averaged between 2010 (the furthest the crash portal goes back) and 2012.
The AAA Foundation study did not attempt to determine if THC was a cause in crashes, according to the report, only that it was involved.
“This study enabled us to review a full 10-years’ worth of data about the potential impact of marijuana on driving safety — and it raises significant concerns,” AAA Foundation for Traffic Safety Executive Director Dr. David Yang wrote in the release. “Results from the analysis suggest that legalization of recreational use of marijuana may increase the rate of THC-positive drivers involved in fatal crashes.”
Eleven states and Washington, D.C., have legalized marijuana for recreational and medical use, while another 22 have legalized it for medical use only, the AAA Foundation reported.