Roadside Survey Finds Changes in Pot Use, Attitudes After Legalization

This article summarizes the findings of a recent Insurance Institute for Highway Safety (IIHS) study of drivers in Washington State who were surveyed about and tested for marijuana use. The authors explored how both attitudes and behavior may have changed in the year since Washington legalized marijuana use. Researchers surveyed drivers (n = 2,355) three times — in June 2014, the month before retail marijuana sales began, in November-December 2014 and in June 2015. Information was collected on Fridays during the day and at night and on Saturday nights. Of the participants completing the survey, 99% also gave saliva or blood to test for THC, the primary psychoactive chemical found in marijuana. The proportion of drivers testing positive for THC increased from 8% before retail sales began to 23% six months after retail sales began; these drivers were tested during the daytime. Among those drivers tested at night, the proportion stayed constant at about 20% before and after retail sales began. The authors consider the differences between these findings and statistics regarding drinking alcohol and driving. Readers are referred to the full research paper (


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  • Media Type: Web
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Filing Info

  • Accession Number: 01672654
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 20 2018 1:39PM