AAA itself admitted in the very same May report that “Researchers examined the lab results of drivers arrested for impaired driving, and the results suggest that legal limits for marijuana and driving are problematic because [there] is no science showing that drivers reliably become impaired at a specific level of marijuana in the blood.” They added that this conclusion distinguishes the influence of cannabis from alcohol-induced impairment, and that “marijuana can affect people differently, making it challenging to develop consistent and fair guidelines”. Their admission that there is currently no scientific evidence of a direct relationship between marijuana use and psychomotor impairment puts a big bold asterisk on the claim of growing “marijuana-related” auto fatalities in Washington and elsewhere. (It’s also notable that it wasn’t technically the national foundation which objected to Prop. 64, but the Automobile Club of Southern California, AAA’s regional chapter).
As journalist Radley Balko wrote in 2014 about a similar Colorado traffic study: “references to ‘marijuana-related’ accidents in studies [could] refer to any measure or trace of the drug. So when officials and legalization opponents talk about increases in these figures, it still isn’t clear what any of this means for road safety.” As for increases in the presence of pot among drivers in fatal accidents, Balko astutely reasoned that “It makes sense that loosening restrictions on pot would result in a higher percentage of drivers involved in fatal traffic accidents having smoked the drug at some point over the past few days or weeks. You’d also expect to find that a higher percentage of churchgoers, good Samaritans and soup kitchen volunteers would have pot in their system. You’d expect a similar result among any large sampling of people. This doesn’t necessarily mean that marijuana caused or was even a contributing factor to accidents, traffic violations or fatalities.”
Recent criticism of RMHIDTA’s reports of legal marijuana’s impacts in Colorado makes the significance of their figures similarly dubious. As Jacob Sullum writes of their latest release, “RMHIDTA’s habit of inviting inferences in headlines while warning readers not to draw them in footnotes reaches ridiculous extremes,” adding “a line graph on page 17 shows a sharp increase in ‘traffic deaths related to marijuana’”, while a footnote warns “That does not necessarily prove that marijuana was the cause of the incident.”
Putting the superficially alarming figures highlighted by Feinstein and Youngblood in the wider context of our current lack of conclusive knowledge about the influence of cannabis on driving ability reveals their logic for opposing Proposition 64 to be far more shaky than their earnestly dire predictions insist. Regardless it is appearing increasingly less likely that public opinion on the measure can be swayed even by the most urgent op-ed in the home stretch of this campaign; an LA Times poll released Tuesday indicates that 58 percent of voters support Prop. 64, with 74 percent of voters aged 18 to 29 endorsing the proposal.