1. Professor, School of Transportation, Southeast Univ., #2 Si Pai Lou, Nanjing 210096, China (corresponding author).
2. Graduate Research Assistant, School of Transportation, Southeast Univ., #2 Si Pai Lou, Nanjing 210096, China.
3. Professor, School of Transportation, Southeast Univ., #2 Si Pai Lou, Nanjing 210096, China.
4. Graduate Research Assistant, Dept. of Civil and Environmental Engineering, Univ. of South Florida, 4202 E. Fowler Ave. ENB118, Tampa, FL 33620.