Wreck on the Highway: The Intersectionality of Driver Culpability, THC, Other Intoxicants and Fatalities in Washington State

Objective: Given the legalization of recreational cannabis in 2012 in Washington State and recent mixed results regarding the effects of cannabis on driver safety, we examine the link between Delta-9-Tetrahydrocannabinols (THC) and driver’s behavior, including speeding and driver errors which may have contributed to a particular fatal crash. Methods: The current study utilized data from the Washington State Fatality Analysis Reporting System Analytical File (WA FARS) in years 2008-2016. A series of logistic regression were employed to compare THC positive and negative drivers, as well as drivers who tested positive for other intoxicants. Results: The results of the study were mixed as Delta-9 THC positively predicted speeding, but not other driver errors. Interestingly, Carboxy THC, a non-psychoactive chemical that can be detected for a longer period of time, was a significant predictor of both speeding and driver errors. Conclusions: This research further demonstrates that cannabis is a risk factor for fatal crashes, though it is not nearly a risk factor of the same magnitude as alcohol. Additional research is needed to better understand why Carboxy THC is a stronger and more robust predictor of poor driving behavior than Delta-9 THC

Relative Risk of Cannabis, Alcohol, and Their Combination on Driver Behavior in Fatal Crashes in Washington State

The greater availability of cannabis following legalization increases the likelihood that more drivers will drive drugged, rendering the determination of its effect on crashes a matter of vital public policy interest. For criminal justice agencies, this issue takes on increased importance, as drugged driving is a criminal offense. We examine the relative risk of cannabis (Delta-9-Tetrahydrocannabinols [hereafter THC]), alcohol, and the combination of the two, on fatal crashes in Washington state, using data from the Washington Coded Fatal Crash (WA-CFC) Files, which includes appended toxicology results. Findings indicate the presence of alcohol or the combination of alcohol and THC in the blood of a driver involved in a fatal crash is more likely to be associated with risky driving behaviors, fatal injuries, and death compared to THC alone