Two recent studies in the U.S. suggest some states where cannabis is legal have seen more crashes on their roadways.

New reports from two American highway safety organizations suggest some of the states where recreational cannabis is legal have seen more crashes than the neighbouring states where it isn’t.

The Highway Loss Data Institute found collision-based insurance claims from Colorado, Nevada, Oregon and Washington rose six per cent from 2012-2017 compared to the neighbouring states -- Idaho, Montana, Utah and Wyoming -- where the drug remains illegal.

The Insurance Institute for Highway Safety found police-reported crashes in the same states rose 5.2 per cent from 2012-2016.

"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," IIHS-HLDI President David Harkey said in a news release. "States exploring legalizing marijuana should consider this effect on highway safety."

The studies do, however, mention that the role of cannabis in these accidents isn’t clear as drivers who test positive for drugs are often found with alcohol in their system as well.

The study also did not include the District of Columbia and the five other states where recreational cannabis is legal: Alaska, California, Maine, Massachusetts and Vermont.

Driving high is illegal across the United States and Canada.