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

Abstract

Given the legalization of recreational cannabis in 2012 in Washington State and recent mixed results regarding the effects of cannabis on driver safety, the paper examines the link between delta-9-tetrahydrocannabinols (THC) and driver behavior, including speeding and driver errors which may have contributed to a particular fatal crash. The current study utilized data from the Washington State Fatality Analysis Reporting System Analytical File (WA FARS) from 2008 to 2016. A series of logistic regressions were employed to compare THC-positive and -negative drivers, as well as drivers who tested positive for other intoxicants. The results of the study were mixed; it was found that delta-9-THC positively predicted speeding, but not other driver errors. Interestingly, carboxy-THC, a non-psychoactive chemical which can be detected for a longer period of time, was a significant predictor of both speeding and driver errors. This research further demonstrates that cannabis is predictive of risky behavior by drivers in fatal crashes, though it is not nearly as strong a predictor as alcohol. Additional research is needed to understand better why carboxy-THC is a stronger and more robust predictor of poor driving behavior than delta-9-THC.