1. Professor, Highway Engineering Key Laboratory of Sichuan Province, School of Civil Engineering, Southwest Jiaotong Univ., Chengdu 610031, China.
2. Research Assistant, Highway Engineering Key Laboratory of Sichuan Province, School of Civil Engineering, Southwest Jiaotong Univ., Chengdu 610031, China (corresponding author).
3. Civil Engineer, Dept. of Traffic Planning and Design, China Railway Siyuan Survey and Design Group Co., Ltd., Hubei, Wuhan 430063, China.
4. Assistant Professor, Highway Engineering Key Laboratory of Sichuan Province, School of Civil Engineering, Southwest Jiaotong Univ., Chengdu 610031, China.