1. School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
2. College of Transportation, Jilin University, Changchun 130022, P. R. China
3. School of Statistics, University of International Business and Economics, Beijing 100029, P. R. China
4. College of Metropolitan Transportation, Beijing University of Technology, Beijing 100124, P. R. China
5. Faculty of Business, University of Greenwish, London SE10 9LS, UK