Car crashes remain the No. 1 cause of death and injury for young people. For most of the past decade, teen crash deaths in the U.S. were on a decline before the trend reversed in 2013. Over those 10 years, we surveyed 109,266 teens at 281 schools in 11 states, to draw a distinction between what young drivers think about safe-driving behaviors vs. what they actually do. What we found was both enlightening and disturbing.