1. Associate Professor, School of Traffic and Transportation, Beijing Jiaotong Univ., Beijing 100044, China (corresponding author).
2. Associate Professor, School of Traffic and Transportation, Beijing Jiaotong Univ., Beijing 100044, China.
3. Professor, School of Traffic and Transportation, Beijing Jiaotong Univ., Beijing 100044, China.
4. Associate Professor, School of Engineering Science, Univ. of Science and Technology of China, Hefei 230026, China.