1. School of Transportation, Southeast University, Si Pai Lou No. 2, Nanjing 210096, China
2. Key Laboratory for Traffic and Transportation Security of Jiangsu Province, Huaiyin Institute of Technology, Huaian 223003, China
3. Program on Chinese Cities, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
4. School of Civil Engineering, Purdue University, West Lafayette, IN 47907, USA