Study On The Small Vehicle Trajectory And Dangerous Sections On Reverse Curves In Mountain Highway

In order to promote the development of countryside in mountainous areas,many mountain roads have been newly built and rebuilt in China in recent years.Restricted by theterrain,the majority of the mountain roads are in a low-grade with numerous continuous curves and frequent traffic accidents.The main reason for the accidents is that the actual vehicle trajectory is not consistent with the expected one.It means that some vehicles are not in their own lane,but tend to near or even cross the central line,resulting in accident.As the important structural form of the continuous curve,the reverse curve is an accident-prone section.Therefore,it is necessary to study the trajectory of small vehicles and the dangerous sections on the reverse curve of mountain roads.Firstly,based on the designed radius of the circular curves in the mountainous area,after actual surveys,six reverse curves of small and large radius combinations were selected as the research objects,and the small vehicles were to be studied.The selected reverse curve consists of two curves and line segments before and after the curve,and line segment between the curve.The speed?curve radius?the cross slope?superelevation??the longitudinal slope and the widening were selected as the influencing factors of the study.Relying on UAV to collect video data,and using Tracker?CAD?matlab and other softwares to obtain velocity and driving trajectory values.Combined the designed parameters with the parameters of the reverse curves obtained from the actual investigation,influencing factor indexes were constructed.Secondly,according to the speed changing curves of all vehicles and average and 85%^th velocity changing curves in each reverse curve,the overall characteristics of the driving speed of each reverse curve were analyzed,which include large radius curves,small radius curvesand three kinds of line segmengt.Meantime,it was found that the line segment between curves has a greater effect on speed of small vehicles.Thirdly,according to the driving trajector changing curves of all vehicles and average and 85%^thdriving trajectory changing curves in each reverse curve,the overall characteristics of the driving trajectory of each reverse curve and the influence to driving trajectory from influencing factors were analyzed.Based on the average speed distribution in different intervals,the dangerous sections formed by the different driving directions and different speed intervals were studied.It was found that the formation of the dangerous sections are mainly related to the left turn of the small vehicle driving in the curve.And the greater velocity is,the easier will it form a larger dangerous section.Finally,the analytic hierarchy process and entropy weight method were applied to determine the influence weight value of each influence index on the relative distance of the driving trajectory formed by different directions.And a comprehensive index is constructed based on the influence weight values,the relationship between the comprehensive influence index and the relative distance is fitted.It was found that the larger comprehensive index is,the smaller the relative distance is.