1. Lecturer, School of Transportation, Shandong Jianzhu Univ., Jinan 250101, China.
2. Professor, Beijing Key Laboratory of Traffic Engineering, Beijing Univ. of Technology, Beijing 100124, China (corresponding author).
3. Associate Professor, Beijing Key Laboratory of Traffic Engineering, Beijing Univ. of Technology, Beijing 100124, China.
4. Professor, Beijing Transportation Institute, Beijing 100161, China.