1. Assistant Professor, Dept. of Transportation and Logistics, Dalian Univ. of Technology, No.2 Linggong Road, Ganjingzi District, Dalian, Liaoning, China 116024.
2. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of North Carolina at Charlotte, Charlotte, NC 28223-0001 (corresponding author).
3. Professor and Director, Center for Transportation Policy Studies, Univ. of North Carolina at Charlotte, Charlotte, NC 28223-0001.