1. Postdoctoral Research Associate, Dept. of Civil and Environmental Engineering, Univ. of Tennessee, Knoxville, TN 37996.
2. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Tennessee, Knoxville, TN 37996 (corresponding author).
3. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Tennessee, Knoxville, TN 37996.
4. Professor, School of Traffic and Transportation, Beijing Jiaotong Univ., Bejing, China, 100044.