THE RESEARCH ARM of AAA says states that set legal limits for marijuana driving impairment have no scientific basis for the standards and urged a national effort to adopt uniform tests to ensure road safety.
“Legal limits for marijuana and driving are arbitrary and unsupported by science, which could result in unsafe motorists going free and others being wrongfully convicted for impaired driving,” the automobile club said in a press release accompanying the release of a wide-ranging study into drivers under the influence of marijuana.
The results are similar to a report last month in CommonWealth that indicated law enforcement officials have no way of accurately measuring whether someone is legally high from marijuana because measurable levels of THC, the intoxicating chemical in pot, can stay in someone’s system for days, even weeks, after use. If someone is a regular marijuana user, the levels can be high even if they have not smoked prior to being tested.
“There is understandably a strong desire by both lawmakers and the public to create legal limits for marijuana impairment, in the same manner as we do with alcohol,” Marshall Doney, AAA’s president and CEO, said in a statement. “In the case of marijuana, this approach is flawed and not supported by scientific research. It’s simply not possible today to determine whether a driver is impaired based solely on the amount of the drug in their body.”
Six states – Colorado, Washington, Montana, Nevada, Ohio, and Pennsylvania – have set per se limits for driving under the influence. Colorado and Washington have legalized recreational use of marijuana; Nevada, Montana, and Pennsylvania allow medical marijuana; Ohio has no legal use for marijuana.
The study examined the results of more than 5,300 people nationwide who were arrested for driving under the influence of marijuana, 600 of whom tested positive for THC only, while the others had THC and other substances. The study says the median level for THC in the drivers’ blood was 4 nanograms per mililiter, which is below the 5 nanogram level used by three of the six states that set limits. Colorado, Washington, and Montana have a 5 nanogram level; Nevada and Ohio set the limit at 2 nanograms; while Pennsylvania has a 1 nanogram threshold.
But, the researchers say, those who tested positive for THC only without alcohol or other drugs performed poorer on standard roadside sobriety tests, even if they had a level below the per se limit. The study also found that some who tested with a level above 5 nanograms passed the sobriety test, indicating they were misclassified based on the standard.
“Based on this analysis, a quantitative threshold for per se laws for THC following cannabis use cannot be scientifically supported,” the study says.
The report, though, was not a win for proponents of legalized marijuana. AAA researchers examined fatal accidents in Washington state since voters there approved legal recreational use of marijuana in 2012.
From 2010 to 2014, there were 3,031 fatal crashes in the state. Roughly 10 percent had some level of THC in their blood, though some had other drugs or alcohol as well. From 2010 to 2013, the first full year of legal marijuana, the rate of fatalities with drivers having THC in their blood was between 7.5 percent and 8.8 percent. In 2014, the number of drivers in fatal accidents who tested positive for THC more than doubled to 17 percent.
“The significant increase in fatal crashes involving marijuana is alarming,” said Peter Kissinger, president and CEO of the AAA Foundation for Traffic Safety. “Washington serves as an eye-opening case study for what other states may experience with road safety after legalizing the drug.”
The study also included a survey of drivers from 2013-2015 who self-reported how long before driving they drank alcohol or smoked marijuana. According to the data, roughly 14 percent of drivers said they got behind the wheel when they were over the legal limit of .08 blood alcohol content while nearly 5 percent said they drove within an hour of smoking pot.
Overall, 58 percent of those surveyed said smoking marijuana within an hour of driving increases the risk of accidents while 3.6 percent said it decreased the risk, with the remainder unsure. However, those who use marijuana were less likely to think it increases the risk and more likely to believe it has no effect or even reduces the risk.
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