1. Ph.D., Transportation Research Center, Wuhan Institute of Technology, Wuhan, Hubei 430073, P.R. China; formerly, Ph.D. Candidate, School of Transportation, Southeast Univ., Nanjing, Jiangsu 210096, P.R. China.
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Pennsylvania State Univ., University Park, PA 16802 (corresponding author).
3. Professor, School of Transportation, Southeast Univ., Nanjing, Jiangsu 210096, P.R. China.
4. Associate Professor, School of Transportation, Southeast Univ., Nanjing, Jiangsu 210096, P.R. China.