1. Professor, School of Highway, Chang’an Univ., S. 2nd Ring Rd., Xi’an 710064, China (corresponding author).
2. Ph.D. Candidate, School of Transportation, Southeast Univ., Nanjing 210096, China.
3. Lecturer, School of Architecture and Civil Engineering, Xi’an Univ. of Science and Technology, Xi’an 710054, China.
4. Lecturer, School of Highway, Chang’an Univ., Xi’an 710064, China.