Research On Roadside Accidents Risk Assessment And Prevention Scheme

In China,roadside accidents account for 40%of fatalities resulting from traffic accidents.Frequent and serious traffic accidents have become a focal issue because they hinder the sustainable development of society.Roadside safety has become an important issue of traffic management departments,and performing research on roadside safety contributes to improving the level of road safety and reducing the number of traffic accidents and fatalities.This paper used PC-Crash simulation soffware to obtain the data of roadside accidents.Based on the experience of roadside accidents investigation and analysis,road geometric design indexes(horizontal curve radius,hard shoulder width,longitudinal slope,superelevation slope,and widen value of curve),pavement condition(adhesion coefficient)and traffic characteristics(vehicle speed and vehicle type)maybe contributing to occurrence of roadside accidents were chosen to carry out simulation test.The chi-squared automatic interaction detection(CHAID)decision tree technique was employed to identify significant risk factors and explore the influence of different combinations of significant risk factors on roadside accidents according to the generated decision rules,so as to propose specific improved countermeasures.On the basis of the significant risk factors,the path analysis method was used to analyze the causative mechanism of roadside accidents under the interaction of multiple indicators of "geometric design condition-pavement condition-traffic condition",and explore the important of different significant risk factors on roadside accidents.Based on the identified significant risk factors,this paper utilized Bayesian network to establish a multivariate model between the probability of roadside accidents and the significant risk factors,and realize the quantitative analysis of roadside accidents probability under the influence of any number(1?5)of risk factor.According to probabilistic prediction results and the idea of cumulative frequency method,the thresholds of road geometric design indexes and road adhesion coefficient corresponding to different vehicle types and operating speeds were given,and the method for roadside accident blackspot identification was put forward.Finally,its validity was verified by the case.To propose corresponding safety measures to reduce accident losses,this paper used the acceleration severity index(ASI)as the indicator of occupant injuries and horizontal radii,vehicle departure speeds,side slope and subgrade height as research variables to carry out collision tests of trucks and cars in the presence or absence of roadside guardrails by constructing the vehicle,road and guardrail model in PC-crash simulation software.For straight and curved segments of highways,the occupant injury evaluation models of trucks and cars were fitted based on the ASI.According to the Fisher optimal segmentation method,reasonable classification standards of severity of roadside accidents and the corresponding ASI thresholds were determined,and were verified by the case.A proportion of trucks was introduced to further improve the ASI evaluation model.Finally,based on the probability and severity of roadside accidents,a risk assessment method for roadside accidents was proposed.According to the identified significant risk factors,speed is the most significant risk factor affecting the occurrence of roadside accidents.Aiming at the section with a high risk of roadside accidents,this paper used Bayesian discriminant technology to construct the discriminant functions of occurrence and non-occurrence of roadside accidents,and given the maximum safe speed calculation model corresponding to different vehicle types,road geometric design indexes and road conditions.Finally,its validity was verified by the case.By exploring the main factors affecting the design of the roadside clear zone width,this paper recorded the movement track of each simulation vehicle after entering the roadside,and calibrated the horizontal distance between the right front side of the vehicle and the edge of the carriage-way to determine the width of the roadside clear zone.Based on the relationship between the slope clear zone width,speed and horizontal curve radius,the recommended values of roadside clear zone width for different operating speed and horizontal curve radii on the straight and curved sections were given,respectively.Given that the limited land resources in China,the setting conditions of roadside clear zone should be discussed before designing the roadside clear zone.According to the road land index,subgrade height and hard shoulder width,and combined with the recommended width of the roadside clear zone,this paper carried out the research on setting conditions of the roadside clear zone.For sections with setting conditions of the roadside clear zone,firstly,based on the occurrence probability model and occupant injury assessment model of roadside accidents,the safety improvement benefit calculation model brought by setting roadside clear zone was constructed,then the additional engineering cost generated by setting roadside clear zone was calculated from the two aspects of project cost and land expropriation.By analyzing the benefit-cost ratio and further evaluating the social stability risk caused by setting roadside clear zone,it is suggested whether the roadside clear zone should be set by a case analysis.