1. School of Civil Engineering, Chongqing Jiaotong University, 400074 Chongqing, P. R. China
2. State Key Laboratory of Fire Science, University of Science and Technology of China, 230027 Hefei, P. R. China
3. Business School, University of Shanghai for Science and Technology, 200093 Shanghai, P. R. China
4. Institute for Theoretical Physics, University of Cologne, Zuelpicher Strasse 77, 50937 Cologne, Germany
5. School of Automotive and Traffic Engineering, Jiangsu University, 212013 Zhenjiang, P. R. China
6. School of Transportation and Logistics, Southwest Jiaotong University, 611756 Chengdu, P. R. China