In July of 2014 Angela Hawken appeared on C-SPAN, and I wrote about it on these pages. See Angela Hawken on C-Span re marijuana legalization.
She talked about the results of her research, and one noteworthy observation was of the complicated relationship between alcohol and marijuana. She said driving while stoned on marijuana is probably not as bad as driving drunk. However, driving after using alcohol and marijuana is worse than driving under the influence of either one alone.
Two and a half years later we see some real world results of the state experiments with marijuana legalization. See States that enact medical marijuana laws see dips in fatal car crashes. Excerpt.
When examining 19 states that had medical marijuana laws on the books by 2014, researchers found that their average rate of traffic deaths fell 11 percent after the laws were enacted. The happy side-effect wasn’t uniform, however; only seven states saw significant reductions, while two states saw increases. Nevertheless, the authors of the new report in the American Journal of Public Health argue that the data bucks the common criticism that more pot access should increase car crashes and injuries.
Drops in traffic deaths may, in part, be explained by people swapping alcohol for pot, leading to reduced drunk driving, the study’s authors speculated. To back that up, the authors note that the lives spared tended to belong to younger people, particularly 25- to 44-year-olds—an age group frequently involved in alcohol-related traffic deaths.
More research is needed. But this study seems to support Ms. Hawken's predictions.
In any event, this is a big win for the federalist theory of allowing states to make their own laws so that those that work can be copied by the other states.