1. Department of Pediatrics, University of Washington, Seattle, Washington, USA.
2. Department of Epidemiology, University of Washington, Seattle, Washington, USA.
3. Harborview Injury Prevention and Research Center, University of Washington, Seattle, Washington, USA.
4. Center for Child Health, Behavior and Development, Seattle Children's Research Institute, Seattle, Washington, USA.
5. Department of Civil and Environmental Engineering, University of Washington, Seattle, Washington, USA.
6. Department of Industrial and Systems Engineering, University of Washington, Seattle, Washington, USA.
7. Department of Neurology, University of Washington, Seattle, Washington, USA.