Editor’s note: This commentary is by Paul Armentano, the deputy director of the National Organization for the Reform of Marijuana Laws (NORML). He co-wrote “Marijuana Is Safer: So Why Are We Driving People to Drink?“.
[V]ermont lawmakers made history earlier this month by becoming the first state to approve legislation depenalizing the adult possession and use of marijuana. But some opponents fear that enacting these changes may pose risks to traffic safety.
Gov. Phil Scott is among those who have expressed concerns, acknowledging : “It’s no secret that I don’t believe this a priority for Vermont. I believe that what we should be doing is trying to find ways to protect those on our highways. … I’ll take a look at the bill. But I’ve been pretty clear that I’d like to see some improvements to the bill to make sure we have structures in place that provide safety to Vermonters.”
One can sympathize with the governor’s position. But a careful review of the available evidence finds that such fears are largely unfounded.
First, it should be stressed that driving under the influence of marijuana is already a criminal offense in Vermont. Nothing in the language of Vermont’s proposed law changes this reality.
Second, scientific studies consistently find that marijuana-positive drivers possess a comparatively low accident risk, particularly when compared with alcohol-positive drivers. In fact, the largest ever controlled trial assessing marijuana use and motor vehicle accidents, published in 2015 by the U.S. National Highway Traffic Safety Administration NHTSA), [reports that marijuana positive drivers possess virtually no statistically significant crash risk compared to drug-free drivers after controlling for age and gender.
By contrast, drivers with detectable levels of alcohol in their blood at legal limits possess nearly a four-fold risk of accident, even after adjusting for age and gender.
First, it should be stressed that driving under the influence of marijuana is already a criminal offense in Vermont. Nothing in the language of Vermont’s proposed law changes this reality.
This finding is consistent with prior meta-analyses of crash risk data. For example, a review of 66 separate crash culpability studies published in the journal Accident Analysis and Prevention reported that THC-positive drivers possessed a crash risk on par with drivers testing positive for penicillin (Odds Ratio: 1.10 for cannabis versus Odds Ratio: 1.12 for penicillin) This risk is far below that associated with driving with two or more passengers (OR=2.2) and is comparable to the difference between driving during the day versus driving at night.
Data from states regulating marijuana use
Further, data from states that have liberalized marijuana’s legal status show no uptick in motor vehicle crashes. Writing in December in the American Journal of Public Health, investigators at Columbia University reported, “[O]n average, medical marijuana law states had lower traffic fatality rates than non-MML states. …. Medical marijuana laws are associated with reductions in traffic fatalities, particularly pronounced among those aged 25 to 44 years. … It is possible that this is related to lower alcohol-impaired driving behavior in MML-states.”
A review of federal FARS data (Fatal Analysis Reporting Systems) further finds that trends in motor vehicle accidents in Colorado and Washington post-legalization are no different than crash trends in non-legalization states over this same period of time.
Use prior to driving should be discouraged
Nevertheless, the governor is correct that use of marijuana prior to driving ought to be discouraged and that better efforts ought to be made to identify drivers who may be under the its influence. These include greater funding for the training of drug recognition evaluators (DREs) and the use of modified roadside field sobriety tests.
These efforts should not include the imposition of per se thresholds for THC or its metabolites, as such limits are not scientifically correlated with driver impairment. As acknowledged by NHTSA, “It is inadvisable to try and predict effects based on blood THC concentrations alone, and currently impossible to predict specific effects based on THC-COOH (marijuana’s primary metabolite) concentrations.”
Efforts should also be made to better educate the public with regard to the existing traffic safety laws, as well as to the evidence surrounding marijuana’s potential influence on driving. In particular, this messaging should stress that combining marijuana and alcohol greatly impacts driving behavior and is associated with far greater risk of accident than the use of either substance alone.
Such an educational campaign was implemented in Canada, where legislation is pending to regulate adult marijuana use nationwide, by the Canadian Public Health Association and could readily be replicated in Vermont.
In addition to increasing public safety, implementing these steps would help assuage concerns that further regulating the adult use of marijuana could potentially lead to an increase in incidences of drugged driving or limit the state’s ability to successfully identify and prosecute such behavior. Gov. Scott should move swiftly to sign Senate Bill 22, but also continue to work with regulators, lawmakers, and traffic safety experts in the coming months prior to ensure that the law is enacted in a way that is responsible and does not inadvertently compromise traffic safety.
