Understanding patterns in Marijuana impaired traffic crashes

Background: The landscape of marijuana regulation is rapidly changing. Several countries have already legalized marijuana in some form, and marijuana for recreational purposes will soon become legal for a quarter of the U.S. population. The potential increase in traffic fatalities due to impaired drivers remains a prominent debate among policymakers and in the media. One recent report stated that the fraction of fatal crashes in which at least one driver tested positive for marijuana has increased nationwide by an average of 10 percent from 2013 to 2016. In Louisiana, crashes involving marijuana have increased by 195% from 2010 to 2016.Methods: This study collected seven years of marijuana impaired crash data from Louisiana to identify the key association factors and their patterns. The research team identified the hidden association patterns of key attributes from the complex crash dataset using the cluster correspondence analysis.Results: The findings reveal several key risk patterns including female drivers at the intersection involved in multiple vehicle right angle crashes, multiple vehicle head-on crashes at two lane roadways with no separation, multi-vehicle rear-end crashes at two-lane roadways with separation, careless single-vehicle crashes, single-vehicle crashes during dark with no streetlights, and open country interstate crashes.Conclusions: The findings of this study can be useful in the coordination of regional and local behavioral safety efforts to lessen the occurrence and injury level of marijuana impaired traffic crashes.