2. Is marijuana consumption really on the upswing? If so, the uptick has nothing to do with the legalization of recreational pot use in Colorado and Washington, since the voters in those states didn't approve legalization until 2012. It could be that pot is more readily available and acceptable now, or it could also be that the tests used to identify it have been getting better over the years. Or it could be both.
At this point, it's far too early to tell what effect, if any, legalized marijuana use will have on traffic fatalities. However, given the growing number of states considering such measures, the research is well worth doing.