Association for Public Policy Analysis & Management

Introduction. Roadway safety is an important potential public safety outcome of cannabis legalization, which many fear will lead to increased impaired driving under the influence of cannabis. But it is possible cannabis legalization may improve road safety instead, for instance, users substitute away from cannabis towards alcohol to cannabis. This study will investigate the net effect in Oregon, exploiting the legalization of registered medical marijuana dispensaries (Measure 80) and the ensuing ramp-up of registered stores from 2014 to present.

Methods. Rates of car crashes will be regressed on the presence of registered marijuana dispensaries in Oregon, controlling for other factors such as Census demographics, the presence of liquor stores and other businesses, and miles traveled on state highways. Models will include 1) cross-sectional analysis for a single time period, controlling for spatial autocorrelation and 2) panel models with time fixed effects applied to 8 year-quarter time periods. To identify heterogeneous associations on crashes under different circumstances, models will be applied to outcome variables including injury crashes, fatal crashes, crashes on weekend nights, and crashed featuring drivers under 21. Currently data available allow for analysis from 2014 to 2015, but data on unregistered medical marijuana stores operating prior to 2014 will be collected manually in further months, allowing for analysis dating back years further. Crash data will be sourced from the Oregon Department of Transit’s Crash Analysis & Reporting Unit. Cannabis store data is recorded by the Oregon Medical Marijuana Dispensary Program.

Results. The study will report results of the various regressions discussed above.

Discussion. Findings will inform assessments of the risks of cannabis legalization, policies regarding detecting and sanctioning cannabis-impaired driving, and regulatory decisions about the appropriate number and placement of cannabis stores.