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

In 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’s 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 delta-9-tetrahydrocannabinol (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 THC-positive 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.

• Record URL:
  http://www.nhtsa.gov/staticfiles/nti/pdf/812299-WashingtonStatedrugstudy.pdf
• Record URL:
  http://www.nhtsa.gov/staticfiles/nti/pdf/812299a-WashingtonStateDrugStudy-appendices.pdf
• 
• Supplemental Notes:
  • Appendices are a separate document (73p.) at provided URL.
• Corporate Authors:

  Pacific Institute for Research and Evaluation

  11720 Beltsville Drive, Ste 900
  Calverton, MD  United States  20705-3111

  National Highway Traffic Safety Administration

  Office of Behavioral Safety Research, 1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Ramirez, Anthony
  • Berning, Amy
  • Carr, Katherine
  • Scherer, Michael
  • Lacey, John H
  • Kelley-Baker, Tara
  • Fisher, Deborah A
• Publication Date: 2016-7

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; Maps; References; Tables;
• Pagination: 73p

Subject/Index Terms

• TRT Terms: Alcohol tests; Alcohol use; Before and after studies; Drivers; Drug tests; Drug use; Drugged drivers; Drunk driving; Laws and legislation; Marijuana; Surveys
• Geographic Terms: Washington (State)
• Subject Areas: Highways; Law; Safety and Human Factors;

Filing Info

• Accession Number: 01609738
• Record Type: Publication
• Report/Paper Numbers: DOT HS 812 299
• Contract Numbers: DTNH22-11-D-00226-0004
• Files: HSL, TRIS, ATRI, USDOT
• Created Date: Sep 1 2016 9:27AM