1. Associate Professor, School of Civil Engineering and Transportation, Univ. of Hohai, Nanjing, Jiangsu 210098, PR China.
2. Professor, School of Transportation, Southeast Univ., Nanjing, Jiangsu 211189, PR China; Professor Emeritus, Dept. of Civil and Environmental Engineering, Louisiana State Univ., Baton Rouge, LA 70803 (corresponding author).
3. Professor, School of Civil Engineering and Transportation, Univ. of Hohai, Nanjing, Jiangsu 210098, PR China.
4. Professor, Dept. of Civil and Environmental Engineering, Univ. of California, Berkeley, CA 94720-1710.