1. Professor, Intelligent Transportation System Research Center, Southeast Univ., Si Pai Lou #2, Nanjing, P.R. China 210096 (corresponding author).
2. Professor, Intelligent Transportation System Research Center, Southeast Univ., Si Pai Lou #2, Nanjing, P.R. China 210096.
3. Associate Professor, Dept. of Civil, Construction, and Environmental Engineering, North Carolina State Univ., Raleigh, NC 27695.