Either the Scots don't like cannabis, or they drive more cautiously on it. That's one conclusion a person might draw from a new study published in the Journal of Forensic Sciences that looked at toxicology reports for driver fatalities after lawmakers decreased the legal blood alcohol limit.
In December 2014, Scotland and New Zealand both enacted new laws that reduced the legal limit from 80mg of alcohol per 100ml of blood to 50mg. The researchers looked at data from fatal car and motorcycle accidents a year before and after the 2014 change, and in Scotland, the new law corresponded with an increase in drugged driving. In other words, many drivers substituted drugs for alcohol in hopes of lowering their chances of getting busted for drunk driving.
There was, however, one statistical outlier: "Scotland [experienced] an increase in drug prevalence among fatally injured drivers and motorcyclists, with the use of all drug groups increasing after the limit change, with the exception of cannabinoids."
Cannabinoids are naturally occurring compounds in cannabis, and they show up in a smoker's toxicology report when they test "positive" for consumption. The finding above suggests that Scots increased their use of all drugs except cannabis following the alcohol-limit change, and those who opted for cannabis arguably saved lives by reducing—or at least not increasing—the number of driver fatalities involving alcohol and other drugs.
New Zealand, in contrast, actually saw a decrease in drugged driving following the alcohol-limit change, while simultaneously noting an increase in deaths for alcohol-only drivers and those who drank and took drugs at the same time.
The takeaway here is not that you should drive stoned instead of drunk or high on opioids, cocaine, shrooms or other drugs. Rather, you should never drive stoned, drunk or high. The bigger message, in fact, is that while many say cannabis legalization will increase vehicular deaths, this study at least suggests it might do the exact opposite.
In related news, a Frontiers in Pharmacology study did a meta-analysis of cannabis use and traffic events, and the researchers concluded that "the overall effect size for driving under the influence of cannabis on unfavorable traffic events is not statistically significant." However, the study did note differences when looking at subgroups and highlighted issues involving cannabis-driving studies, including "the indiscriminate employment of the term 'cannabis use'" and the need for "objective data regarding marijuana usage" and "a clinical assessment of the impairment."