Behavioral impact of graduated driver licensing on teenage driving risk and exposure.

Graduated driver licensing (GDL) is a critical policy tool for potentially improving teenage driving while reducing teen accident exposure. While previous studies demonstrated that GDL reduces teenage involvement in fatal crashes, much remains unanswered. We explore the mechanisms through which GDL influences accident rates as well as its long term effectiveness on teen driving. In particular, we investigate: (1) whether GDL policies improve teenage driving behavior, or simply reduce teenage prevalence on the roads; (2) whether GDL exposed teens become better drivers in later years. We employ a unique data source, the State Data System, which contains all police reported accidents (fatal and non-fatal) during 1990-2005 for 12 states. We estimate a structural model that separately identifies GDL's effect on relative teenage prevalence and relative teenage riskiness. Identification of the model is driven by the relative numbers of crashes between two teenagers, two adults, or a teenager and an adult. We find that the GDL policies reduce the number of 15-17-year-old accidents by limiting the amount of teenage driving rather than by improving teenage driving. This prevalence reduction primarily occurs at night and stricter GDL policies, especially those with night-time driving restrictions, are the most effective. Finally, we find that teen driving quality does not improve ex post GDL exposure.