1. Graduate Research Assistant, School of Transportation, Southeast Univ., Si Pai Lou #2, Nanjing 210096, China.
2. Professor, School of Transportation, Southeast Univ., Si Pai Lou #2, Nanjing 210096, China (corresponding author).
3. Associate Professor, Dept. of Civil and Environmental Eng., Univ. of Nevada, Reno, NV 89557.
4. Professor, School of Transportation, Southeast Univ., Si Pai Lou #2, Nanjing 210096, China.