Thats all complete lies. The CO DPS stats show just the opposite.
+1 and (since your a traffic guy and I'm and auto claims guy...) I will add: the fatality crashes have gone up in CO sure, but... so has both the population AND the total miles traveled on CO roads. So we'd expect fatal collisions to rise, absolutely. If you extrapolate the rate of crash fatalities per capita OR per miles traveled OR over miles traveled per capita, I'd bet it ends up pretty damn flat (though I didn't whip out Excel and enter any data).
Attributing any increase/decrease of fatal crashes on marijuana through such methods as noted in the article is just grasping at straws to promote some narrative.