Paul Armentano: Drugged driving concerns should not influence marijuana decision

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?“.

Vermont 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, “On 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.

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  • Denise Valenti

    With legal adult use of marijuana comes responsibility. Since those consuming drugs or alcohol are not always acting in a responsible manner, there needs to be greater public health and legislative action to protect the public if there is legal use of marijuana for recreation.
    The data on marijuana impairment and driving is often inconsistent. More and better studies need to be done. The state of Washington recognized this and worked with private agencies to survey the crash and fatality rates. They separate out alcohol, psychoactive THC and inactive THC in their survey/reports with fatal crashes. What is clear is that the fatality rate specific to cannabis, both active and inactive forms of THC–has increased. Another chilling statistic: Those testing positive for marijuana alone, not alcohol or other drugs, are FIVE TIMES more likely to kill someone other than themselves compared to a driver testing positive for alcohol. In general, those that are drunk usually kill themselves, those that are stoned kill others. While the number of drivers positive for marijuana and involved in fatal crashes were fewer than with alcohol, the number of innocent victims killed by the marijuana drivers were greater. This is certainly demonstrating that marijuana impaired driving is more dangerous than alcohol for the public in the state of Washington.
    Until there are tests of function to correlate with a biologic such as blood or saliva, the best line of defense are those professional law enforcement officers trained in drug impaired detection such as RIDE or DRE. Again, data is muddy, but the state of Oregon did not have the dramatic increase in marijuana specific road fatalities. They also have the highest ratio of DRE trained officers per population…in the nation. Perhaps all should study what Oregon did right. Funding to train more officers related to DRE or ARIDE will contribute to saving lives.
    Tests of function are desperately needed so as to obtain convictions and remove the dangerous drivers from the road. IMMAD – Impairment Measurement Marijuana and driving is a simple app for a tablet that objectively measures functional impairment. It measures the visual field deficits (HUGE BLIND SPOTS or TUNNEL VISION) that occurs with marijuana use. Marijuana has been shown to significantly impair the eye retinal ganglion cells. IMMAD – Impairment Measurement Marijuana and Driving, measures this. IMMAD and other tests of function need to be further developed and studied so as to have better tools for law enforcement to use in dealing with marijuana impaired driving.

  • Michael Milburn

    The data that Mr. Armentano cites is very persuasive–the hysteria about marijuana-impaired driving is unnecessary. Additionally, an issue that opponents of legalization raise is how to measure impairment from marijuana. Per se laws specifying a level of THC in the blood (e.g., 5 ng/mL) from which impairment can be inferred are not supported by science, according to the National Highway Traffic Safety Administration. Actual impairment should be measured.
    I have developed a new public health app that measures impairment–it is called DRUID (an acronym for “DRiving Under the Influence of Drugs”) available now in the Apple App Store (Android version coming soon). DRUID measures reaction time, decision making, hand-eye coordination, time estimation and balance, and then statistically integrates hundreds of data points into an overall impairment score. DRUID takes just 5 minutes (and the 2-minute version will be part of the DRUID app shortly).

    Our website is

    DRUID allows marijuana users (or others who drink alcohol, use prescription drugs, etc.) to self-assess their own level of impairment and (hopefully) decide against driving if they are impaired. Prior to DRUID, there was no way for an individual to accurately assess their own level of impairment. DRUID also demonstrates that it is feasible to measure impairment reliably by the roadside, not just exposure to a drug.

    DRUID was recently featured on NPR’s All Things Considered:

    Also on television:

    After obtaining my Ph.D. at Harvard, I have been a professor of psychology at UMass/Boston for the past 40 years, specializing in research methods, measurement and statistics.

    Michael Milburn, Professor
    Department of Psychology

    • Peter Everett

      Michael, for those of us who graduated before the merger, it’s Boston State…not U Mass Boston!

      • Michael Milburn

        I understand and appreciate your loyalty to Boston State. I was hired in 1978 at UMB. The merger came a few years later. Massachusetts is one of the lowest in per capita spending on public higher education in the country. Boston State should still be around.

    • Leonard Frieling

      Precisely my point. We’ve worked with an app My Canary along the same lines. Science paper is at and we too look to reaction time, balance, etc., and compare the results of the 4 modules to the users “baseline” performance. Is the person’s reaction time what it generally should be for that person? We don’t care if they are tired from eating turkey or impaired by their regular pain medication. They either are performing adequately or they are not, and if not, should not be using a hydraulic forge or driving a car or working as an aircraft patroller. I may think that no one under 25 should be allowed to drive. That does not mean it is a good idea or that it is supported by science. Claiming that it does is simply building a house on mud and complaining that the foundation is not solid.

      • Michael Milburn

        The MyCanary app was a good start. As an advance, DRUID includes “divided attention tasks”; gives an actual overall impairment score, not just a green, yellow, or red light; and DRUID gives an estimate of the comparable blood alcohol level for the person’s level of impairment. And DRUID costs 99 cents versus $2.99 for MyCanary.

        • Leonard Frieling

          Thanks! Agreed. It was a good “start.” My partner Mark Silverman had been working on it for some time, so we were beyond just a “start,” and I understand your comment and agree. Thanks for taking the time to reply. $0.99 is a better price for sure. We avoid the “comparable BAC” for the obvious reasons. Your version looks like a nice step forward. Of course you see the divided attention aspect to what we’ve done so far. Again, thanks for the feedback.

    • Leonard Frieling

      Marc Silverman’s expertise (study, experience, etc.) includes NASA, professional athletes, etc., with the emphasis on behavior, mental and physical performance, including medical applications.

  • Edward Letourneau

    The bill should have had a little provision added to state that if you can’t get a job because you can’t pass the drug test — then there is no welfare for you. That would keep the druggies under self-control.

    • David Bell

      Better yet, why not make poor people do 20 hours a week of forced community service; we can call it a poverty tax. The GOP dream come true.

    • Leonard Frieling

      Should such testing include not hiring, or firing, people who are positive for prescription pain pills, used according to good medical advice? What about those that are physically or mentally handicapped? Should not the focus be “does any of the behavior, drug use or not, impair the person to any degree which has significance to their effective and safe performance of the job? I don’t want an impaired Uber driver. I don’t care if the impairment is caused by alcohol, any legal or illegal drug, or even by the lack of sleep and the anger from a family squabble. Want to test something? Test performance! Test reaction time! Test coordination appropriate for the job. Or we can continue to base these life-altering decisions on folk tales, outdated government politics and propaganda, etc. Remember that our US Government was begging farmer to grow hemp during WWII. We could not outfit our ships later in the war since Manila Hemp out of the Philippines was no longer available. Steel is fine, but to tie up, hemp rope was essential. Columbus (and all other sailing ships until at least the mid-1880s I believe) had hemp sails. Every one. Only propaganda ended US production of hemp after WWII, since it looked in many ways and is botanically close to psychoactive cannabis sativa. Hemp is cannabis sativa also. Please consider reading more before continuing the spread of incorrect outdated and harmful information paraded as science. Look to the state of medical research on THC in Israel. They may well lead the world in medical research with marijuana. The results continue to be life-saving for a wide range of patients.

  • Catherine Antley

    Marijuana triples the risk of getting into a car crash
    – Since WA legalized, AAA reported a doubling in marijuana-related fatalities (recent marijuana use)
    – Drugged driving incidents for MJ have also climbed in Colorado
    – As more people use marijuana, more instances of drugged driving – and other negative consequences – inevitably follow
    – Studies finding “states with MMLs have lower car accidents” fail to control for the many confounding factors.
    When does an adult in the room say ” I drive better stoned” ?
    NORML, the organization Paul Armentano works for, is actively trying to undermine drugged driving standards in legal (and other) states. Mr. Armentano is the head of a group that will financially benefit if legalization passes. As has been the case thoroughout this debate at the Vermont statehouse, those with a repeatedly undisclosed financial incentive have dominated the conversation because their finanacial backing gives them time and means to do this.. skewing and misrepresenting the misinformation in their favor.. Isn’t Vermont better than this?

    • Leonard Frieling

      Sorry. These “claims” are simply untrue. When we look in blood for red cells, we’d find them. We could then say “red cells are now present and were not before” because we never looked for them before. The conclusion simply does not follow. Mr. Armentano is in ways “the head” of a group that puts itself out of business when legalization passes everywhere. Our goal (YES I am a life member of the NORML Legal Committee, former judge, teacher, advocate, writer, etc. with a world-wide reputation in the field of drug law, drug chemistry, and societal drug use impact) is to put ourselves OUT of business. A business lawyer succeeds if they keep you as a client forever. As a criminal defense attorney, I am doing best if I never see a client again because they don’t need me. As an advocate we do the best if we solve the problem and are never needed again. We could then shift our advocacy focus to other issues ranging from fighting world hunger to any other worthy subjects for our contributions to the well-being of society. And in these new areas to which we’ll be able to shift our efforts we will continue to base our teaching and lobbying on facts, the best research, the most accurate history, etc. I respectfully suggest that Ms. Antley do the same in her efforts. Of course we need not agree. We should both base our positions on reality and go from there. Time spent learning what is real and what is fiction is quite important.

  • Denise Valenti

    Many substances cause impaired driving as well as actions. Physical and sensory dysfunction can prevent a person from driving safely and there are restrictions on driving or mandated cessation of driving if impairments are considered severe enough to impact driving. Marijuana uses creates an impairment to drive. As a clinician having specialized for over thirty years in physical and sensory impairment and driving, it is alarming to note that the use of marijuana is causing preventable deaths. Marijuana certainly is not safer than other substances including alcohol, just different.

    The data out of the state of Washington reports an increase in fatal crashes specific to marijuana. What is chilling is that they are also reporting a greater harm to innocent pedestrians, bicyclist and other drivers when compared to alcohol.
    Those testing positive for marijuana alone, not alcohol or other drugs, are FIVE TIMES more likely to kill someone other than themselves compared to a driver testing positive for alcohol.

    Tests of function are desperately needed so as to obtain convictions and remove these dangerous drivers from the road. IMMAD – Impairment Measurement Marijuana and driving is a simple app for a tablet that objectively measures functional impairment. It measures the visual field deficits (HUGE BLIND SPOTS or TUNNEL VISION) that occurs with marijuana use. Marijuana has been shown to significantly impair the eye retinal ganglion cells. IMMAD – Impairment Measurement Marijuana and Driving, measures this. IMMAD and other tests of function need further development and studied so as to have better tools for law enforcement to use in dealing with marijuana impaired driving.

  • Leonard Frieling

    Keep in mind that in most situation etoh, drinking alcohol, is also present, and frequently in large amounts. Historically THC might have been present but until recently we were rarely testing for it. Now, while the presence of THC is being reported, the presence of alcohol, even in high doses, is not mentioned. The elephant in the room is being ignored while we look at what’s in the ash tray on the coffee table. NO potentially impairing substance, whether it is etoh ethyl alcohol, THC is relevant levels, or any of the variety of licit and illicit substances, and even lack of sleep, should be present in amounts that can impair driving. Alcohol and some prescription drugs remain far and away the “real” problem worthy of our attention.

  • Lori Robinson

    It’s really outrageous to read this commentary, but as a growing # of parents who have lost their teen or young adult offspring to the consequences of today’s potent strains and byproducts of THC-marijuana, should Paul Armentano’s words surprise us? No, we’ve come to expect nothing but illogical arguments from the pot INDUSTRY.

    Here’s the most recent report from the state that first legalized recreational pot:
    Monitoring Health Concerns Related to Marijuana in Colorado, 2016. Section 2, pages 145-156 “Driving and Marijuana”.
    Let’s use the facts, not NORML’s mistruths.

    • Richard Kennedy

      Losing a child is the ultimate nightmare for any parent but I just read pages 145-156 of the Colorado report and there is nothing in them that contradicts anything in Mr. Armentano’s article. The CO report says there is “substantial” evidence that marijuana impairs driving ability, but it has no data on the extent of that impairment, much less on how it compares with alcohol. The main point of Mr. Armentano’s article is that marijuana impairs driving ability much less than alcohol, and he presents data from several other studies to support that conclusion.
      Personally I think the most compelling study was one mandated by the French government, which ordered that all drivers involved in a fatal accident in France from October 2001 through September 2003 be tested for drugs. That provided a database of over 10,000 drivers for whom it was known how much of what drug was in their system, and whether they had caused the accident. From that information they calculated the “odds ratio” of how much marijuana or alcohol increased a driver’s chance of causing a fatal accident. For drivers with highest amount of THC (above 5 nanograms) the odds ratio was 3.06, slightly below the 3.30 ratio for drivers with blood alcohol content less than 0.05 (well below the US DUI standard of 0.08). For drivers with the highest BAC–above 0.20–the odds ratio was 40! Go to:

  • MikeParent
  • MikeParent



  • Jason Brisson

    Great commentary! Very hopeful that the reefer madness mistruths/illogicalness/hysteria does not win!

  • John farrell

    You can study this issue till the cows come home and the results will be the same
    regardless of all the “Reefer Madness” proponents out there. If the Gov vetoes the bill
    over 80,000 Vermonters will remain criminals.