1. School of Instrument Science and Engineering, Southeast Univ., Nanjing 211189, China; Southeast Univ., Wuxi Campus, Wuxi 214082, China.
2. Research Scientist, Transportation System and Mobility Group, Argonee National Laboratory, Lemont, IL 60439.
3. Professor, Dept. of Civil, Architectural and Environmental Engineering, The Univ. of Texas at Austin, Austin, TX 78712 (corresponding author).