Does One Size Fit All?: Reimagining Sobriety Testing for Marijuana Use and Traffic Safety

One of the biggest roadblocks to marijuana legalization in states where it is still criminalized and illegal to consume without a medical permit is how states will handle people driving under the influence of marijuana. The Governors Highway Safety Association, a non-profit organization located in Washington, D.C., reports that there are two basic methods that states tend to use when addressing drug-impaired driving: “zero tolerance” laws that make it illegal to drive with any measurable amount of specified drugs in the body and per se laws that make it illegal to drive with amounts of specified drugs in the body that exceed set limits.[1] Sixteen states have zero tolerance laws in effect for one or more drugs and five states have per se laws in effect for one or more drugs.[2]

            In Commonwealth v. Gerhardt, 81 N.E.3d 751 (Mass. 2017), the court discussed that THC is “known to have an impact on several functions of the brain that are relevant to driving ability, including the capacity to divide one’s attention and focus on several things at the same time, balance, and the speed of processing information. While not all researchers agree, a significant amount of research has shown that consumption of marijuana can impair the ability to drive.” It would be irresponsible to treat marijuana as a “harmless” drug and not consider the possible negative side effects on traffic safety, but it is equally as irresponsible to believe that marijuana could not be regulated the same way as alcohol. A study commissioned by AAA’s safety foundation said it is not possible to set a blood-test threshold for THC, which can reliably determine impairment.[3] However, PBS News Hour reports “There’s no science that shows drivers become impaired at a specific level of THC in the blood. A lot depends upon the individual. Drivers with relatively high levels of THC in their systems might not be impaired, especially if they are regular users, while others with relatively low levels may be unsafe behind the wheel.”[4]

            There are marked similarities in the way that impairment of alcohol and marijuana differ from person to person. The Texas A&M Health Science Center reports that alcohol is metabolized at vastly different rates from person to person depending on factors such as body size, metabolism, tolerance, dependence, and binge drinking.[5] Since these factors are already accounted for in sobriety tests for alcohol impairment, therefore, why is it unreasonable to think that a similar protocol could not be developed for marijuana? Of course, people of different sizes and levels of tolerance will display different levels of impairment based on their consumption, so maybe it’s time to make traffic safety laws not so “one-size-fits-all.”

[1] Drug Impaired Driving, GHSA (Last visited December 9, 2020)

[2] Id.

[3] Andrew Gross, Fatal Crashes Involving Drivers Who Test Positive for Marijuana Increase After State Legalizes Drug, AAA Newsroom (January 30, 2020) (Last visted December 9, 2020)

[4] State laws that regulate driving while using marijuana are flawed, says AAA, PBS News Hour, (May 10, 2016) (Last visited December 9, 2020)

[5] Dominic Hernandez, You Asked: Why Do People React Differently to Alcohol? Texas A&M Health Science Center, (February 28, 2018) (Last visited December 9, 2020)

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