Road crashes have increased by as much as six percent in Colorado, Nevada, Oregon and Washington, compared with neighboring states that haven’t legalized marijuana for recreational use, according to new research from the Insurance Institute for Highway Safety (IIHS) and Highway Loss Data Institute (HLDI).
Colorado and Washington were the first states to legalize recreational marijuana for adults aged 21 and older with voter approval in November 2012. Retail sales began in January 2014 in Colorado and in July 2014 in Washington. In Oregon retail sales of legalized recreational marijuana began in October 2015, followed by Nevada in July 2017.
HLDI analysts estimate that the frequency of collision claims per insured vehicle year increased by a combined six percent following the start of retail sales of recreational marijuana in Colorado, Nevada, Oregon and Washington, compared with the control states of Idaho, Montana, Utah and Wyoming. The combined-state analysis is based on collision loss data from January 2012 through October 2017.
Analysts allowed for differences in the rated driver population, insured vehicle fleet, the mix of urban versus rural exposure, unemployment, weather and seasonality.
“The new IIHS-HLDI research on marijuana and crashes indicates that legalizing marijuana for all uses is having a negative impact on the safety of our roads,” said IIHS-HLDI President David Harkey. “States exploring legalizing marijuana should consider this effect on highway safety.”
In addition to the study states, Alaska, California, Maine, Massachusetts, Vermont and the District of Columbia also allow recreational use of marijuana for adults 21 and older and medical use of marijuana. Another 22 states allow medical marijuana, while 15 more states permit the use of specific cannabis products for designated medical conditions. Legalization of recreational use is pending in New Hampshire, New Jersey, New York and Pennsylvania. In November, Michigan and North Dakota will hold referendums on marijuana, and Missouri and Utah voters will decide whether to expand medical marijuana laws in their states.
Driving under the influence of marijuana remains illegal in all 50 states and D.C., but the IIHS points out that determining impairment is challenging. Unlike alcohol, the amount of marijuana present in a person’s body doesn’t consistently relate to impairment.
“Despite the difficulty of isolating the specific effects of marijuana impairment on crash risk, the evidence is growing that legalizing its use increases crashes,” Harkey added.