1. Texas A&M Transportation Institute, The Texas A&M University System, Austin, TX, USA;
2. Texas A&M Transportation Institute, The Texas A&M University System, College Station, TX, USA;
3. School of Public Health, Dept. of Health Promotion and Behavioral Sciences, Michael and Susan Dell Center for Healthy Living, University of Texas Health Science Center-Houston, Houston, TX, USA;
4. Department of Medicine, Environmental Health Service, Section of General Internal Medicine, Baylor College of Medicine, Houston, TX, USA;
5. Michael and Susan Dell Center for Healthy Living, University of Texas Health Science Center-Houston, Houston, TX, USA;
6. Dept. of Kinesiology and Health Education, University of Texas at Austin, Austin, TX, USA