1. Department of Epidemiology, University of North Carolina, Chapel Hill, Chapel Hill, North Carolina;
2. Injury Prevention Research Center, University of North Carolina, Chapel Hill, North Carolina;
3. Highway Safety Research Center, University of North Carolina, Chapel Hill, North Carolina;
4. Department of Surgery, University of North Carolina, Chapel Hill, North Carolina;
5. Carolina Center for Health Informatics, Department of Emergency Medicine, University of North Carolina, Chapel Hill, North Carolina