1. School of Transportation Science and Engineering, Room B7319, Harbin Institute of Technology, Harbin 150090, CN, e-mail: hitdzj@hit.edu.cn
2. School of Transportation Science and Engineering, Room B7311, Harbin Institute of Technology, Harbin 150090, CN
3. Dept. of Civil and Environment Engineering, Room 104, Washington State Univ., Pullman, WA 99163, US.