Two reports conclude collisions have surged over 5% in states that have legalized marijuana recreationally.
A recent report from the Highway Safety (IIHS) and Highway Loss Data Institute (HLDI) claims that car accidents have increased in states where marijuana has been legalized. Two studies were put forward by the groups. The IIHS study used data from collisions reported to insurance agencies. The HLDI study used data from police reports, which includes cars uninsured in accidents. Both reports conclude accidents have increased by over 5% in states that have newly legalized the substance.
HLDI finds that collision claims per vehicle rose by 6% following recreational legalization in Colorado, Nevada, Oregon and Washington, compared with the control states of Idaho, Montana, Utah and Wyoming. Differences in the rated driver population, insured vehicle fleet, the mix of urban versus rural exposure, unemployment, weather and seasonality were accounted for in the study.
The second study conducted by IIHS included just three states--Oregon, Washington and Colorado. The IIHS looked at collision data from police reports between 2012–16, before and after retail sales in those states, finding a 5.2% increase in collisions. Researchers compared Colorado with Nebraska, Wyoming and Utah, and they compared Oregon and Washington with Idaho and Montana.
Both studies do not draw a direct correlation to accidents and marijuana use, but the president of the institutes David Harkey calls it a “solid indicator” that marijuana is the cause. Other factors make the report’s findings complicated. Testing for marijuana is not cut and dry. A positive test for the drug could mean that the driver was intoxicated with the substance at any point three weeks prior. Also, marijuana is commonly used with other substances such as alcohol. Nonetheless, as more states legalize the drug, it’s possible accident rates climb accordingly.