Ask safety experts what makes American roads so dangerous and they tend to reduce it down to three simple words: belts, booze, and speed. Of course, there are other contributors to traffic deaths. An improving economy has more people commuting to work by car. Mobile technology has led to a serious spike in distracted driving. And, in many parts of the U.S., a crumbling infrastructure makes the simple act of driving more dangerous. But those three perennial problems are the main causes behind a shocking 14% increase in traffic deaths in America from 2015 to 2017—amounting to more than 40,000 deaths per year.