1. School of Transportation, Southeast University, Nanjing 211189, China http://orcid.org/0000-0002-7963-9370 (T.M.)
2. School of Transportation, Southeast University, Nanjing 211189, China (Corresponding author), e-mail: guangji_xu@seu.edu.cn http://orcid.org/0000-0001-5716-5226