Please use a scientific method before drawing conclusions that confirm your predisposition. Deaths per mile driven have fallen at the same rate in the years before 2014 and the years after. If pot smoking were making the roads more dangerous, where's the evidence? Look at the charts and pay attention to the dashed lines. They are adjusted for miles driven to take into account the increased traffic from a strong economy and considerable increase in the population.

https://www.codot.gov/news/documents/safety-press-conference-boards-jan-31-2017