Marijuana advocates question the study's comparison of states with such varied populations.
Rocky Mountain Insurance Information Association is an industry group that covers Colorado, Wyoming, Utah and New Mexico.
The researchers also examined pre-legalization data in Colorado, Washington, and Oregon. "The HLDI's findings on the early experience in Colorado, Oregon and Washington should give other states eyeing legalization pause".
As Gregor Bister of CNBC noted, "While Moore's research finds a greater crash risk, his study does not say if the increase in collisions in the three states were directly caused by drivers who were high."
In both states, marijuana legalization eliminated one of the major justifications used by police officers to stop motorists, cutting searches by more than 40 percent after legalization.
"It would be hard to say that marijuana is a definitive factor, lacking a citation, in a significant number of crashes to say that what we're seeing here is a trend", noted Kenton Brine, president of the Northwest Insurance Council, a group that represents insurance companies in Washington, Oregon, and Idaho.
Fair enough. After all, determining the role that THC in the driver's blood played in a deadly crash is hard. The one maintaining that collisions are up comes from the Highway Loss Data Institute, while the other offering appears in the latest edition of the American Journal of Public Health.
After retail marijuana sales began in Colorado, the increase in collision claim frequency was 14 percent higher than in nearby Nebraska, Utah and Wyoming.
Washington saw a more than 6 percent increase, and OR had a more than 4.5 percent increase.
It's important to highlight that the study focused on crashes, not injuries or fatalities.
Since 2012, eight states have passed voter-approved ballot measures legalizing the purchase and possession of marijuana for anyone 21 and older. Researchers compared year-over-year changes in motor vehicle crash fatality rates - on a basis of per-billion vehicle miles traveled - to rates in Alabama, Indiana, Kentucky, Missouri, South Carolina, Tennessee, Texas and Wisconsin.
"I think that if Oregonians and other states looking to legalize cannabis see the whole picture they'll see that regulating, legalizing and taxing cannabis is a better policy than prohibition", Johnson said.