1. School of Traffic & Transportation, Chongqing Jiaotong University, Chongqing 400074, China
2. School of Civil & Transportation Engineering, Qinghai Nationalities University, Xining 810007, China
3. School of Information Science & Engineering, Chongqing Jiaotong University, Chongqing 400074, China
4. Intelligent Transportation System Research Center, Southeast University, Nanjing 210096, China