Car accidents are happening more frequently in states that have fully legalized marijuana, according to researchers.
The Insurance Institute for Highway Safety announced the finding in two new studies that were set to be released on Oct. 18.
“The last thing in the world that we want is to introduce another legal substance where we may be adding to that toll and to the carnage on our highways,” David Harkey, president of the Insurance Institute, told Bloomberg.
“With marijuana impairment, we’re just now starting to understand what we don’t know.”
The study said that the frequency of collision insurance claims in Colorado, Nevada, Oregon, and Washington state rose about six percent higher than in nearby states where marijuana is still illegal.
A separate study by the institute found a five percent increase in the rate of crashes per million vehicle registrations in Colorado, Oregon, and Washington versus nearby states.
Analysts controlled for differences in the rated driver population, insured vehicle fleet, the mix of urban versus rural exposure, unemployment, weather, and seasonality, the institute said.
“The bottom line of all of this is that we’re seeing a consistently higher crash risk in those states that have legalized marijuana for recreational purposes,” Harkey said.
Marijuana Affects Drivers
A number of studies have confirmed that marijuana use negatively affects drivers, including causing a slower reaction time when drivers must respond to unexpected events, such as situations where they need to slam on the brakes; causing problems with switching lanes properly; and impaired cognitive performance, according to a review of the research by the National Highway Transportation Safety Administration sent to Congress in July 2017 (pdf).
According to other studies reviewed by the administration, marijuana is the second most frequently detected drug in crash-involved drivers behind alcohol.
Researchers know a lot about the direct link between alcohol and car crashes but are still working on defining the nature and scope of how marijuana contributes to crashes, the report noted.
The institute’s report came just days after the National Transportation Safety Board announced its finding that a crash that killed 12 people in Texas in March 2017 was caused by a 20-year-old driver’s failure to control his vehicle due to using marijuana and misusing prescription medication.
The driver swerved his pick-up truck into the opposite lane and caused a head-on crash.
Witnesses told authorities the driver had been driving erratically for more than 15 minutes before the crash.
Investigators found marijuana cigarettes in the truck as well as drug paraphernalia and prescription medication, and a toxicology test detected THC and clonazepam, a sedative, in the driver’s system.
The board called for the National Highway Traffic Safety Administration to help identify countermeasures that can help with the growing problem of drug-impaired drivers on the road, including developing an oral fluid screening device that can be used by police officers during traffic stops.
“The pick-up truck driver in this crash made terrible choices with tragic consequences,” said board Chairman Robert Sumwalt. “But the rising tide of drug-impaired driving did not begin with this driver, and it will not end with him. Law enforcement needs additional tools and advanced training to detect impaired drivers before they crash, regardless of the impairing drug they’re using.”