1. Senior Researcher, New Transportation Innovative Research Center, Korea Railroad Research Institute, 176, Cheoldo bangmulgwan-ro, Uiwang-si, Gyeonggi-do 16105, Republic of Korea (corresponding author).
2. Assistant Professor, Dept. of Civil and Environmental Engineering, Utah State Univ., 4110 Old Main Hill, Logan, UT 84322.
3. Assistant Professor, Dept. of Mathematics and Statistics, Utah State Univ., 3900 Old Main Hill, Logan, UT 84322.