Driving Drunk vs. Driving Stoned
Since the legalization of cannabis either medicinally or recreationally in a majority of the states, the number of drivers on the road under the influence of cannabis has inevitably risen as well. Consequently, there have been a variety of laws adopted in these states that make driving under the influence of cannabis (much like alcohol) a criminal offense. However, cannabis and alcohol are two entirely different drugs that affect the body and the brain in different ways, so determining a driver’s level of impairment using methods similar to alcohol isn’t a valid measure. In fact, studies suggest driving under the influence of cannabis is not as dangerous as driving drunk.
Problems Determining Level of Impairment
When it comes to testing a driver’s degree of impairment due to alcohol, blood alcohol content has been shown to be a fairly accurate measure of impairment, which are proportional. In other words, the higher the blood alcohol content, the higher the level of impairment.
By contrast, determining how impaired a driver is due to cannabis is much more difficult. There is currently no nationwide standard for testing cannabis impairment while driving, so this has been something left up to the individual states to determine. In Colorado, for example, a driver with 5 nanograms of delta-9 tetrahydrocannabinol (THC) per milliliter of blood can be prosecuted for DUI. However, unlike alcohol, there is no linear correlation between a person’s THC level and their level of impairment. In addition, THC stays in the bloodstream for weeks, so its presence in a person’s blood is not an accurate measure of current impairment.
Studies
A handful of studies done on this subject suggest that driving stoned is not as dangerous as driving drunk and may even be as safe as driving sober once other variables are accounted for.
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In a 2013-2014 National Highway Traffic Safety Administration (NHTSA) survey, it was found that while drunk driving dramatically increases the chances of getting into an accident, there was no evidence to suggest the same was true for cannabis. Similarly, in a 2015 study by the NHTSA, it was found that drivers who use cannabis are at a significantly lower risk for crash than drivers who use alcohol.
In terms of the number of automobile collisions, a 2017 study published in the American Journal of Public Health found that fatal automobile collisions have not risen in states where cannabis has been legalized, compared with states where it remains criminalized.
In a 2017 report by NHTSA, it states the odds of being involved in a crash immediately after using cannabis are significantly less than being involved in a crash after drinking alcohol.
The explanation being that alcohol makes drivers more aggressive and accident prone, whereas drivers who are high on cannabis are more likely to drive too slowly.
A federal report to Congress (also conducted by the NHTSA) came to similar conclusions in 2017, which found stoned drivers were more cautious, exhibiting “reduced mean speeds, increased time driving below the speed limit and increased following distance during a car following task.”
Most recently, a study in 2021 found that smoking CBD-heavy cannabis had “no significant impact” on driving ability, despite the fact that all study participants exceeded the per se limit for THC in their blood.
It’s fair to conclude studies and reports from the last decade have consistently shown that driving under the influence of cannabis is not as dangerous as driving under the influence of alcohol. This is not to suggest that driving stoned is completely safe and risk-free, but when compared to alcohol, it appears to be relatively much safer. Furthermore, our current and varied methods across the states for determining how impaired a driver is under the influence of cannabis are neither adequate or scientifically sound. For this reason, a more accurate means of measuring a person’s level of impairment from cannabis are needed for these laws to be justifiably enforced.
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