There have been a handful of studies done recently on the number of drivers who have tested positive for cannabis in their system, specifically looking at traffic deaths from the Fatality Analysis Reporting System (FARS) which logs blood test results and gives insight to what drugs were in a driver's system. But conflicting studies that used the same FARS data show that determining cause for marijuana-related traffic accidents can be quite hazy.

In a University of Oregon study published in October 2012, states that legalized pot saw a significant decrease – 8-11% – of traffic fatalities within the first year. Within five years there was a 15 percent decrease, according to the study. The study analyzed all states with legalized medical marijuana laws including the District of Columbia, and also found that those states were more likely to have reduced traffic crimes in general.

However, a similar study published this year by Columbia University, using the same data, found that although traffic fatalities have decreased, the number of people who test positive for cannabis in their system had tripled. Within six states that test blood results within an hour of traffic fatalities, 12% of drivers had marijuana in their system in 2012, three times more than in 1999.

Insurers are staying out of it

The two sides of the same coin has proved nightmarish for law enforcement, trying to determine when a driver is legally impaired, but the debate over “drugged-driving” isn't likely to impact insurance companies trying to differentiate alcohol versus marijuana-related accidents.

“Insurance companies set their rates on claim severity over a period of time. Talking about drugged driving, insurance companies look at any impairment whether driving drunk, medication or legal marijuana,” Carole Walker, executive director for the Rocky Mountain Insurance Information Association tells PC360. “The case becomes what constitutes 'intoxication?'”

But that issue, Walker says, is left more to law enforcement than it is for insurers who are trying to set states' rates.

“For insurance companies, this is still an emerging issue. From the insurance company perspective, if you get a ticket for DUI and it's under the influence of marijuana, that will certainly impact your rates the same as if it were alcohol,” Walker says.