The Effect Evaluation And Improvement Of Setting Position Of Single-point Overspeed Capture In Highway

Speeding is one of the main causes of expressway traffic accidents,and it is also one of the major factors that cause large and serious traffic accidents.In order to reduce traffic accidents caused by speeding,a variety of traffic engineering measures have been applied to road sections that overspeed is frequent and prone.Among them,single-point overspeed capture is a common method to control speed and ensure safety of freeway.However,the effect of reducing speed and improving safety is uneven due to the blindness of setting up.Therefore,the effect of single-point overspeed capture's location would be evaluated and the reasons for this effect would be analyzed deeply,which could provide theoretical basis for improving the setting effect and reference for promoting the level of road traffic safety services.Firstly,the safety effect before and after setted was evaluated directly and concretely.Taking the absolute accident rate and the equivalent accident rate as the index of effect evaluation,the number and the intensity of total traffic accidents,collisions(collision between vehicles and central separation zone or side guardrail,excluding rear-end collision)and rear-end traffic accidents were analyzed emphatically based on the traffic accident data obtained in the section which was affected by the single-point overspeed capture under the influence of single-point overspeed capture,which provides a reference for the targeted improvement of some kind of multiaccident or easy-to-happen traffic accident.Secondly,considering the characteristics of driver recognition,combining with automobile dynamics and adapting principle of energy conservation,the optimization model of single-point overspeed capture for setting position was constructed.According to the model,the relationship between the setting position of single-point overspeed capture and the change of rear-end accident was analyzed in depth.It is to the conclusion,the number and intensity of rear-end accidents would be reduced if the location was consistent with the model.However,the number or intensity of rear-end accidents would be increased if the location is not consistent with the model.Then,the improvement effect of the model and interval velocity capture was compared and analyzed.The improvement research and effect evaluation were carried out by adapting the model or changing the single-point overspeed capture as the interval velocity capture respectively,for the section where the absolute accident rate or the equivalent accident rate of rear-end accident increased after setted.It is found that,the model was superior to the interval velocity capture in reducing the number and intensity of total accidents,the interval velocity capture was superior to the model in terms of reducing the number and intensity of collision accidents,the interval velocity capture was slightly better than the model in the aspect of reducing the number of rear-end accidents,the difference of effect between the two methods were similarly in the aspect of reducing the intensity of rear-end accident.Moreover,the relationship between improvement effect in the section where position was appropriate and road alignment was analyzed in depth.Considering the complex spatial characteristic of road alignment,the spatial road alignment was extracted from the angle of alignment continuity,physical property,visual continuity and driving comfort,and then the characteristic index of spatial road alignment was constructed.By the method of regression analysis,the relationship between the improvement effect of proper position and the indexes was excavated under the influence of single-point overspeed capture.It is found that the single-point overspeed capture and the equilibrium of longitudinal alignment promoted together to the number and the intensity of total accidents,the number and the intensity of collision accidents.That was,the more balanced longitudinal alignment was,the better the reduction effects of single-point overspeed capture on the number and intensity of total traffic accidents and collision accidents were.The single-point overspeed capture and the coordination of plane-vertical combined alignment weakened each other in terms of the number of total traffic accidents and the number and the intensity of collision accidents.That is,the more uncoordinated the plane-vertical combined alignment was,The better the reduction effects of single-point overspeed capture on the number of totle accidents and the number and the intensity of collision accidents were.The singlepoint overspeed capture and the equalization of longitudinal alignment weakened each other's effect on reducing the number of rear-end accidents.That is,the more uneven the longitudinal alignment was,the better the reduction effects of single-point overspeed capture on the number of rear-end accidents was.At last,some suggestions were put forward to improve the setting of single-point overspeed capture in different road sections.The model could be applied to work in the section where the number or the intensity of rear-end accidents increased after the setting and the road alignment varied greatly.The interval velocity capture could be applied to work in the section where the number or the intensity of rear-end accidents reduced after the setting and the road alignment was integrally similarly.