Although teen drivers make up a small percentage of the U.S. driving population, they are at an especially high risk of being involved in a crash. Factors that contribute to teen drivers' risk include their lack of experience and their tendency to engage in unsafe behaviors such as speeding, driving aggressively, or using a cell phone while behind the wheel. To help teen drivers stay safe on the road, we developed the Teen Driver Support System (TDSS), a smartphone- based system that provides real-time, in-vehicle feedback to teens about their risky behaviors--and reports the behaviors to parents via text message if teens don't heed the system's warnings. The TDSS provides geographically specific, real-time feedback to a teen driver at the time unsafe driving behavior occurs so that behaviors can be immediately corrected. This report documents a 12-month field operational test of the system involving 300 newly licensed teens driving on Minnesota roads. The test included a control group that received no feedback, a treatment group that received only TDSS in-vehicle feedback, and a second treatment group that received both TDSS in-vehicle and TDSS parental notifications. Research results indicate an overall safety benefit of TDSS, demonstrating that in-vehicle monitoring and driver alerts, coupled with parental notifications, is a meaningful intervention to reduce the frequency of risky driving behaviors that are correlated with novice teen driver crashes. In particular, the system was shown to be an effective strategy for reducing excessive speeds when used with parental feedback and potentially even without parental involvement.