1. School of Transportation, Southeast University, No. 2 Southeast University Road, Nanjing 211189, China.
2. Department of City and Regional Planning, The University of North Carolina at Chapel Hill, New East Bldg., CB 3140, Chapel Hill, NC 27599, USA.
3. School of Automotive and Traffic Engineering, Jiangsu University, No. 301 Xuefu Road, Zhenjiang 212013, China.