1. Research Institute of Highway Ministry of Transport, Beijing 100191, China.
2. School of Electronic and Information Engineering, Beihang Univ., Beijing 100191, China; Hefei Innovation Research Institute, Beihang Univ., Hefei 230012, China.
3. School of Transportation Science and Engineering, Beihang Univ., Beijing 100191, China.
4. School of Electronic and Information Engineering, Beihang Univ., Beijing 100191, China.