1. College of Transportation, Jilin Univ., No. 5988, Renmin St., Changchun, Jilin 130022, China.
2. Professor, College of Transportation, Jilin Univ., No. 5988, Renmin St., Changchun, Jilin 130022, China (corresponding author).
3. Master′s Candidate, College of Transportation, Jilin Univ., No. 5988, Renmin St., Changchun, Jilin 130022, China.