Chem Tales: We Don’t Yet Know the Dangers of Driving High 

New studies reveal that cannabis may not be putting our roads at risk.

When it comes to regulated cannabis, several legislators have compared the process to building a plane as it flies through the air. The image accurately describes the industry’s state of flux, with pivotal issues of banking access and the fate of compassionate-care programs up in that proverbial air. Another matter that remains controversial is the question of driving under the influence of cannabis.

As reported in this column last March, the most crucial aspect of this argument concerns the need for an objective way to determine if someone has “too much” THC in their system. Developing such a system of measurement has been no easy task, given the many factors involved. One of the chief obstacles on that front is how to establish a baseline. Considering that potency is proportional to tolerance, the same amount of cannabis may pack a wallop for one consumer but barely scratch the surface for another.

Obviously, these matters are relevant to conversations about drinking and driving as well, but given that alcohol has never been posited as a legitimate medicine, it’s far more difficult to take issue with an arbitrary blood alcohol level being used to establish intoxication. In the case of cannabis, however, new information continues to emerge that points overwhelmingly against the validity of a “legal limit” when it comes to pot.

According to AAA’s 2018 Traffic Safety Culture Index, a national survey of more than 2,500 U.S. motorists found that 81 percent of respondents favored laws to make it “illegal to drive with a certain amount of marijuana in your system.” This is perfectly understandable. Anyone who has a history of consuming pot has likely found themselves in a position where turning the key in the ignition would be downright dangerous. The real question? Whether anyone who’s feeling that high is actually getting on the road.

On May 13, the Congressional Research Service released its findings on the matter in a report entitled “Marijuana Use and Highway Safety.”

“Levels of impairment that can be identified in laboratory settings may not have a significant impact in real world settings,” the study’s authors concluded, “where many variables affect the likelihood of a crash occurring. Research studies have been unable to consistently correlate levels of marijuana consumption, or THC in a person’s body, and levels of impairment. Thus, some researchers, and the National Highway Traffic Safety Administration, have observed that using a measure of THC as evidence of a driver’s impairment is not supported by scientific evidence to date.”

At a moment when the researchers commissioned by lawmakers themselves are questioning the validity of testing drivers for THC, it seems fruitless to rely solely on that option as a means of identifying who is too impaired to be on the road.  Furthermore, there’s little — if any — evidence to suggest that those who consume cannabis are more likely to get into a traffic accident.

In a study published this spring, Kansas State University graduate student Andrew Young sifted through 23 years of data on average traffic fatalities to ascertain whether traffic deaths increase after a state legalizes cannabis. As first reported by Kyle Jaeger of Marijuana Moment, the results of Young’s study found “no statistically [significant] relationship between marijuana legalization and fatal crashes.”

Though Jaeger cautions that Young’s study was limited in scope by focusing only on states with legalized recreational cannabis — as opposed to states with medical programs — this data certainly seems to suggest that the notion of drivers getting stoned and losing control may be unfounded. In contrast, the Baltimore Sun reports that from 2017-18, “marijuana-related crashes nearly doubled from 34 to 60 [in Maryland].” All in all, it’s probably still too soon to draw iron-clad conclusions about impairment — and no satisfactory answers should be expected until we can establish a valid method for determining if someone is too high to drive.

A study published in Cannabis Science and Technology last week succinctly summarizes the situation. In his synopsis, “The Holy Grail for Law Enforcement: Accurate Roadside Testing for Driving While Stoned” author David Hodes cuts to the heart of the matter in noting that, in all likelihood, “a device that can accurately measure THC intoxication to the satisfaction of both science and law enforcement is still years away.”

What such an invention might look like — thus far several efforts to create a reliable cannabis breathalyzer have yet to pan out — is difficult to imagine. What matters now is how we choose to address the issue of driving under the influence of cannabis while we wait for a more palatable solution. Surely, there must be some answer other than relying on the observations and honesty of law enforcement, but what that answer is remains to be seen.


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