1. Assistant Professor, Dept. of Road and Railway Engineering, Beijing Univ. of Technology, Beijing 100124, P.R. China (corresponding author).
2. Research Assistant, Dept. of Road and Railway Engineering, Beijing Univ. of Technology, Beijing 100124, P.R. China.
3. Professor, Dept. of Intelligent Transportation, Beijing Univ. of Technology, Beijing 100124, P.R. China.
4. Assistant Professor, Dept. of Civil Engineering, Aswan Univ., Aswan Governorate 81542, Egypt, P.R. China.
5. Professor, Dept. of Civil and Environmental Engineering, Michigan Technological Univ., Houghton, MI 49931.