1. Beijing Key Laboratory of Traffic Engineering and College of Metropolitan Transportation, Beijing University of Technology, 100 Pingleyuan, Chaoyang District, Beijing 100124, China.
2. College of Business Administration, Capital University of Economics and Business, 121 Zhangjiakou Road, Huaxiang, Fengtai District, Beijing 100070, China.
3. School of Civil and Environmental Engineering, Oklahoma State University, Stillwater, OK 74074, USA.