This work is supported by the National Natural Science Foundation of China (Nos. 61772087, 61702052), the Science and Technology Service Platform of Hunan Province (No. 2012TP1001), the Open Research Fund of Hunan Provincial Key Laboratory of Intelligent Processing of Big Data on Transportation (No. 2015TP1005), the Changsha Science and Technology Planning (Nos. KQ1703018, KQ1706064), the Research Foundation of Education Bureau of Hunan Province (Nos. 12C0010, 17A007), the ZOOMLION Intelligent Technology Limited Company (No. 2017zkhx130). We are grateful to anonymous referees for useful comments and suggestions.