Notable new research and commentary on marijuana reforms and traffic fatalities

The JAMA Internal Medicine journal has this week published online notable new original research and commentary on roadway fatalities in some states that have legalized marijuana use by all adults (called RCL in the works).  Here is the main piece and its main results and conclusions from its abstract:

"Association of Recreational Cannabis Laws in Colorado and Washington State With Changes in Traffic Fatalities, 2005-2017":

Results

Implementation of RCLs was associated with increases in traffic fatalities in Colorado but not in Washington State.  The difference between Colorado and its synthetic control in the post-RCL period was 1.46 deaths per 1 billion vehicle miles traveled (VMT) per year (an estimated equivalent of 75 excess fatalities per year; probability = 0.047).  The difference between Washington State and its synthetic control was 0.08 deaths per 1 billion VMT per year (probability = 0.674).  Results were robust in most sensitivity analyses.  The difference between Colorado and synthetic Colorado was 1.84 fatalities per 1 billion VMT per year (94 excess deaths per year; probability = 0.055) after excluding neighboring states and 2.16 fatalities per 1 billion VMT per year (111 excess deaths per year; probability = 0.063) after excluding states without MCLs.  The effect was smaller when using the enactment date (24 excess deaths per year; probability = 0.116).

Conclusions and Relevance

This study found evidence of an increase in traffic fatalities after the implementation of RCLs in Colorado but not in Washington State.  Differences in how RCLs were implemented (eg, density of recreational cannabis stores), out-of-state cannabis tourism, and local factors may explain the different results.  These findings highlight the importance of RCLs as a factor that may increase traffic fatalities and call for the identification of policies and enforcement strategies that can help prevent unintended consequences of cannabis legalization.

And here are two follow-up pieces published with this main piece:

Invited Commentary: "Reducing Impaired Driving Fatalities: Data Need to Drive Testing, Enforcement, and Policy"

Research Letter: "Change in Traffic Fatality Rates in the First 4 States to Legalize Recreational Marijuana"