Correlation ≠ Causation . This article seems to imply that "Marijuana" use is causing these crashes, but it can be detected in the blood weeks or even months after being used. Alcohol is much more dangerous on the road, and this is likely to produce an unnecessary onslaught of reefer madness propaganda. 

Tourists who have been traveling to this state after legalization in droves - who are unfamiliar with the landscape, and sometimes bad winter weather conditions are a much more affecting factor in my opinion.