1. School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Changsha, People's Republic of China
2. Department of Industrial Systems Engineering and Management, National University of Singapore 1, Singapore, Singapore
3. School of Management and Engineering, Nanjing University, Nanjing, People's Republic of China
4. School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan, People's Republic of China