1. Associate Professor, School of Qilu Transportation, Shandong Univ., No. 12550 East Second Ring Rd., Jinan, Shandong 250002, PR China (corresponding author).
2. Professor, School of Qilu Transportation, Shandong Univ., No. 12550 East Second Ring Rd., Jinan, Shandong 250002, PR China.
3. Researcher, Highway Bureau, Shandong Province Transport Dept., No. 19 Shungeng Rd., Jinan, Shandong 250002, PR China.
4. Postgraduate, School of Qilu Transportation, Shandong Univ., No. 12550 East Second Ring Rd., Jinan, Shandong 250002, PR China.