The Insurance Institute for Highway Safety (IIHS) found, in a new study published Thursday, that traffic accidents are up 6% in four states where recreational use of marijuana has been legalized.
Earlier in the week, the National Transportation Safety Board (NTSB) issued a press release about a 2017 traffic accident linked to the "use of marijuana in combination with the misuse of a prescription medication" that killed 12 in Texas.
"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 IIHS's Highway Loss Data Institute told Bloomberg. "With marijuana impairment, we're just now starting to understand what we don't know."
In a separate interview with NBC, Harkey said the new reports do not confirm there is a direct risk by the use of marijuana among motorist, but certainly raises caution flags, especially since law enforcement has limited ways to test drivers if they are under the influence of THC, the active ingredient in marijuana.
"It's certainly early in the game," Harkey told NBC News. But he warned: "We're seeing a trend in the wrong direction."
The IIHS study notes that after retail sales of recreational cannabis began, the frequency of collision insurance claims in Colorado, Nevada, Oregon, and Washington rose about 6%, however, this trend was not observed in surrounding states where marijuana is illegal.
Another IIHS study shows a 5% increase in the rate of auto crashes per one million vehicle registrations reported to police in Colorado, Oregon, and Washington versus neighboring states that have not legalized the drug, reported Bloomberg.
"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 told Bloomberg.
There are now 30 states that have legalized medical marijuana, with Oklahoma recently joining the ranks. Recreational marijuana is legal in California, Alaska, Maine, Massachusetts, and Vermont.
The most recent Gallup poll shows near record-high support for legalizing marijuana in the US, as more states are set to follow, including Michigan, where recreational pot use is on the November ballot.
Gallup poll results show Americans are craving pot, with an explosion in acceptance since the financial crash of 2008:
- Americans' support for marijuana legalization was at a record high of 64% in Gallup's most recent update in October 2017. This represents a continuing increase in support for legalization over the past several decades, with half or more generally favoring it since 2011.
Since the legalization wave began, safety experts have been trying to quantify the potential impact on highway safety, as two IIHS studies show traffic accidents in legal pot states have increased. With so many more states set to allow recreational marijuana use, regulators, law enforcement, and medical authorities need to address the future challenges of stoned drivers on America's highways.