The AAA Position: Marijuana’s Effect on Driving

The AAA Position: Marijuana’s Effect on Driving

The AAA Position: Marijuana’s Effect on Driving

This election year, voters in five states will decide whether to legalize recreational marijuana use. Among them are California with Proposition 64 and Maine with Question 1. Any states that do will join the four others where the drug is already legal for recreational use. The AAA Foundation for Traffic Safety analyzed cannabis use by drivers in one of those states, Washington, and found that the proportion of drivers involved in fatal crashes who had recently used marijuana more than doubled after Washington legalized the drug for recreational use. In addition, there’s currently no easy way to test whether a driver is impaired by marijuana: Unlike alcohol, it can’t be determined by breath or blood tests.

After alcohol, marijuana is the most common drug found in drivers who have been involved in traffic collisions.Marijuana’s main psychoactive ingredient, active-THC, affects key parts of the brain, which can lead to:


Difficulty paying attention


Difficulty staying in traffic lane


Slower reaction times


Difficulty judging distances


Slower decision-making


Reduced peripheral vision


Reduced coordination

 Research results are mixed, but some studies have found that using marijuana as much as doubles a driver’s risk of crashing.2 Furthermore, research shows that drivers killed in crashes who tested positive for marijuana were 1.29 to 6.6 times more likely to have caused the collision.3

A Worrying Trend in Washington State

In 2012, Washington voters approved Initiative 502 to legalize recreational marijuana use for adults. It took effect in December of that year. AAA examined drug tests and fatal crashes among Washington drivers between 2010 and 2014 and found the following:

Percentage of Washington drivers involved in fatal crashes who had recently used marijuana

8% in 2013

17% in 2014

After legalization, the proportion of fatal crashes that involved marijuana more than doubled.

While the data analyzed for the study did not include enough information to determine which driver was at fault in a given crash, the trend is troubling because the proportion of fatal crashes involving marijuana in Washington had been relatively stable between 2010 and 2013.

Determining Impairment Isn’t Easy

To combat marijuana-related crashes, some states have instituted “per se” legal blood limits on active-THC. Washington instituted one as part of Initiative 502, and four other states have them as well.

Per se limits make it a crime to drive with more than a certain amount of a drug in one’s system. Drunk driving laws are a well-known example: In the U.S., driving with a blood alcohol concentration above 0.08 percent is automatically a crime. That’s because decades of research have established a well-understood relationship between how much alcohol is in someone’s blood and their risk of crashing.

Per se limits work for alcohol, because we can reliably predict crash risk from blood alcohol concentration.

They do not work for marijuana, however, for several reasons:

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There’s no evidence that drivers definitively become impaired at a specific level of active-THC in the blood. Some individuals with high blood active-THC levels may not be significantly impaired, whereas others with low levels may still be severely affected.

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There’s currently no way to quickly determine active-THC levels. AAA found that it takes more than two hours on average to collect a blood sample, which means high active-THC levels may decline significantly before they can be measured.

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Marijuana is metabolized in the body differently from person to person. Frequent users can exhibit persistent blood active-THC long after active use, while occasional users may see their levels decline much more rapidly.

Per se legal limits on marijuana intoxication while driving are well-intentioned, but they’re not supported by scientific evidence. Instead, they’re likely to result in unsafe drivers being cleared and unimpaired drivers being convicted.

AAA’s Position

AAA opposes measures to legalize recreational marijuana use, and recommends a “no” vote on both California’s Proposition 64 and Maine’s Question 1. We have a genuine traffic safety concern related to the legalization of recreational marijuana use. It has taken generations to educate the public about drinking and driving and to strengthen the laws to reduce drunken driving. These measures would create new traffic safety issues and increase the problem of impaired driving.

The AAA Foundation for Traffic Safety’s recent research raises many concerns about whether we are prepared to address the traffic safety risks Proposition 64 and Question 1 pose. More studies are needed before making such a far-reaching policy change that could have unintended, but tragic, consequences for traffic safety.

1 “Trends in alcohol and other drugs detected in fatally injured drivers,” Brady, 2014.
2 “Acute cannabis consumption and motor vehicle collision risk,” Asbridge, Hayden, and Cartwright, 2013.
3 “Cannabis effects on driving skills,” Hartman and Heustis, 2013.

Information taken from “Fatal Road Crashes Involving Marijuana Double After State Legalizes Drug,” May 10, 2016, AAA Foundation for Traffic Safety.

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Paul Ebeling

Paul A. Ebeling, polymath, excels in diverse fields of knowledge. Pattern Recognition Analyst in Equities, Commodities and Foreign Exchange and author of “The Red Roadmaster’s Technical Report” on the US Major Market Indices™, a highly regarded, weekly financial market letter, he is also a philosopher, issuing insights on a wide range of subjects to a following of over 250,000 cohorts. An international audience of opinion makers, business leaders, and global organizations recognizes Ebeling as an expert.

6 Responses to "The AAA Position: Marijuana’s Effect on Driving"

  1. Jay Minger   October 9, 2016 at 10:12 am

    Hmmm… You would think AAA would support REDUCING HARM, instead of increasing harm with the status quo of Prohibition.

    Legalize. Tax. Regulate. Educate. Reduce harm.

  2. Linda Taylor   October 19, 2016 at 4:20 pm

    Marijuana is linked to testicular cancer, a decrease in sperm production, pre diabetes in adulthood, a rare form of childhood cancer – Acute Nonlymphoblastic Leukemia (ANLL), an array of breathing disorders and disease including lung cancer, COPD, emphysema, and asthma. It is linked to serious irreversible mental illness including schizophrenia, it lowers IQ, is the number 1 reason for teens entering rehab, has tripled fatal traffic accidents, is linked to heart attacks and strokes, damages neurotransmitters in the brain – Dopamine and Seratonin -(Dopamine is a naturally occurring hormone and neurotransmitter in our brain that is responsible for feelings of happiness, motivation, joy, pleasure, and an overall sense of well being. It also regulates focus and attention levels. Serotonin is a neurotransmitter that is responsible for mood stability and balance.) Marijuana causes depression, anxiety and paranoia. What part of the word “h a r m” don’t these people understand?

    • Chris Turner   October 21, 2016 at 8:23 pm

      You write that “Serotonin is a neurotransmitter that is responsible for mood stability and balance” in an obvious reference to the popular serotonin-as-the-happiness-molecule theory launched and marketed by corporate medicine.

      Yet a sizable volume of sound research studies demonstrated that increasing serotonin and tryptophan either with drugs or supplements (not food because food’s unlikely to significantly raise serotonin) is linked to brain dysfunction, stress hormone release, cognitive deficits, inflammation, impaired blood circulation in the brain, hypertension, cancer, and other less than “happy” effects –

      The “serotonin-happiness” mantra, just like the mechanistic simplistic “chemical imbalance” idea, seem to be almost entirely an all-too convenient invention of the medical-pharma business, which allowed them to sell their highly profitable antidepressant drugs, such as SSRIs.

  3. Linda Taylor   October 19, 2016 at 4:26 pm

    Harm reduction is a dangerous strategy that would teach drug users how to use ‘responsibly’.

    Read about it here…

  4. Linda Taylor   October 19, 2016 at 4:27 pm

    Don’t buy the marijuana lie. Vote NO on Prop 64!

    • Paul Ebeling   October 20, 2016 at 3:29 am

      Linda, I believe you are right on the recreational side of the issue. On the medical side I believe there is valid reasoning. All the best, Paul

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