While recreational dispensary openings in Colorado counties led to increased marijuana-related hospital visits, they were not associated with increases in traffic crash incidents.
Traffic safety researchers, policymakers, and anyone interested in legalization and driving safety.
No traffic crash increase despite confirmed rise in cannabis use
What the researchers found
Using county-level variation in when recreational dispensaries opened across Colorado, the entry of cannabis retail stores was associated with a significant increase in marijuana-related hospital discharges but no increase in traffic crash incidents. At 90% confidence, a large increase in crashes (>5%) could be ruled out.
Why it matters
Traffic safety is one of the most cited concerns about cannabis legalization. This county-level analysis finds no evidence that dispensary openings increased crashes, despite confirming increased cannabis use.
The numbers in context
Significant increase in marijuana-related hospital discharges after dispensary entry. No significant increase in traffic crashes. Upper bound of 5% increase can be ruled out at 90% confidence.
How the study worked
Difference-in-differences analysis exploiting variation in the timing of recreational dispensary entry across Colorado counties. Used marijuana-related hospital discharges as a measure of cannabis use intensity. County-level traffic crash data.
What this study cannot tell us
County-level analysis cannot capture individual-level behavior. Hospital discharges may not perfectly proxy cannabis use. Short post-entry periods in some counties.
How to read the evidence
Rigorous econometric design using natural variation, though county-level ecological analysis has inherent limitations.
When this study was published
Published in 2022.
The bigger picture
The dissociation between increased cannabis use (confirmed by hospital data) and stable crash rates suggests that factors like substitution away from alcohol or increased awareness of impairment may offset driving risks.
Questions still open
- Are cannabis users substituting away from alcohol (which is more strongly linked to crashes)? Would effects differ in the long term as dispensary density increases?
Common questions
Did cannabis dispensaries increase traffic crashes?
Why might crashes not increase?
Read the original research
Does expanding access to cannabis affect traffic crashes? County-level evidence from recreational marijuana dispensary sales in Colorado.
Health economics, 31(10), 2244-2268
Citation
Gunadi, Christian. (2022). Does expanding access to cannabis affect traffic crashes? County-level evidence from recreational marijuana dispensary sales in Colorado.. Health economics, 31(10), 2244-2268. https://doi.org/10.1002/hec.4573