Marijuana, Other Drugs, and Alcohol Use by Drivers in Washington State

NHTSA - Behavioral Safety Researchhttps://doi.org/10.21949/15257952016PDFTech ReportRamirez, AnthonyBerning, AmyCarr, KatherineScherer, MichaelLacey, John H.Kelley-Baker, TaraFisher, Deborah A.Pacific Institute for Research and EvaluationUnited States. National Highway Traffic Safety Administration. Office of Behavioral Safety ResearchInsurance Institute for Highway SafetyUnited States. National Highway Traffic Safety Administration. Office of Behavioral Safety ResearchWashingtonMarijuanaAlcohol useImpaired driversDrug useTestingData collectionBefore and after studiesNightDOT HS 812 299DTNH22-11-D-00226-0004In Washington State legal sales of marijuana began July 8, 2014. A voluntary, anonymous roadside study was conducted to assess the prevalence of drivers testing positive for alcohol and other drugs, including marijuana, on Washington\u2019s roads. Data was collected in three waves, before implementation of legal sales, about 6 months after implementation, and 1 year after implementation.Of the almost 2,400 participants who provided an oral fluid or blood sample, 14.6 percent of drivers, 19.4 percent of drivers, and 21.4 percent of drivers were THC-positive in Waves 1, 2, and 3, respectively. There were no statistically significant differences between waves. There was a statistically significant increase in daytime prevalence of THCpositive drivers between Wave 1 (7.8%) and Wave 2 (18.4%), and also between Wave 1 and Wave 3 (18.9%). There was an increase in the percentage of THC-positive nighttime drivers with each successive wave, but these increases were not statistically significant. Synthetic marijuana was found in only 2 of the participants.129