First, this is a well-done article. Second, correlation is not causation. The somewhat sensational headline suggests more than correlation. The body of the article takes a more nuanced approach. As more people consume pot, more will have measurable amounts long after the psychoactive components have worn off, so the numbers will go up even if the drivers involved in fatal accidents are not high at the time of the crash.  CO and WA - among others - must pool their abundant pot-tax resources and conduct comprehensive, evidence-based analysis of the impacts of THC on driver (and other) behaviors.  Driving while impaired is a problem - assuming that drivers who've consumed THC are dangerously impaired at some measurable level during some measurable time after consumption. But the article admits that many of those involved in fatal accidents could have consumed THC long before, and it shows other substances involved, too.  This article is largely speculative, and we need real evidence.