But with the wave of change comes new research linking legal cannabis with an increase in vehicle crashes.

"The likelihood of being involved in a collision in states with legalized marijuana is higher than neighboring states we used as controls," said David Harkey, IIHS-HLDS president.

The report analyzed insurance and police data from some of the first states to legalize recreational cannabis -- Colorado, Washington, Oregon, and Nevada.

In those states, crashes are up by as much as six percent compared with states where marijuana is illegal.

"We do not want to see marijuana reach the same level of destruction on our roadways as we have seen with alcohol," said Harkey.

While drunk driving is widely considered taboo, the same stigma may not exist for driving high.

In a Washington roadside survey, drivers who tested positive for THC were less likely to agree that marijuana impairs driving.

Fourteen-percent of drivers with marijuana in their system had a child in the car.

"You shouldn't be behind the wheel regardless of what the substance is," Harkey said.

Driving under the influence of marijuana is illegal in all 50 states, but determining impairment continues to be a challenge.

Researchers say states considering legalization should consider the potential impact on highway safety.

Recreational marijuana is pending in New Jersey, New York, New Hampshire, and Pennsylvania; marijuana referendums are on the ballot in Michigan and North Dakota this November.

More than 60-percent of Americans say they support marijuana legalization, according to the Pew Research Center.