Study On Traffic Safety Assurance Technology For Superelevation Transition Section Of Multi-lane Expressway Under Rainy Condition

With the increasing concern of society on traffic safety,the frequent occurrence of rainy traffic accidents on expressway has gradually attracted attention.Rainfall mainly affects road visibility and the situation of pavement water accumulation.When driving on a rainy day,the visibility of expressway decreases and the view obstacle of drivers’ increases.A large amount of rainfall would make the rain remained on the pavement and resulted in water accumulation,which can cause the formation of water film on the road surface,reduce the adhesion ability between the driving vehicle tires and the ground.As the final result,vehicle water sliding can occur,which is prone to traffic accidents.Through investigation,it has been found that expressway traffic accidents on rainy days usually occur on the road sections with a composite slope of less than 0.5%,especially the place which is near the superelevation transition zero slope section outside the flat curve.With the increase in the number of expressway lanes,traffic accidents also present an increasing trend.Therefore,in order to reduce the possibility of water accumulation in the superelevation transition sections outside the flat curve,it is of great significance to study the optimal design and traffic safety guarantee technology of superelevation transition sections for multi-lane expressways under rainfall conditions.It can also help to improve expressway traffic safety and the level of service.The paper firstly uses mathematical statistics methods to first investigate and analyze the collected traffic accident data from Zhejiang expressways.And the characteristics of traffic accidents on rainy days are obtained.Based on the alignment conditions and the spatial distribution of traffic accidents on the Taijin Expressway,it is found that the superelevation transition sections are the rainy accident-prone sections.Then,on the basis of summarizing the research status at home and abroad,the impacts of rainfall on vehicle anti-sliding performance and drivers are analyzed,and the impacts of rainy visibility and pavement water accumulation on traffic safety are studied.The regression models among the maximum water film thickness of the superelevation transition section and the longitudinal gradient,rainfall intensity,superelevation gradient rate and the length of the flow path is obtained by using simulation in the aided design system Hint CAD.Besides,the regression models among the longest water flow path and the longitudinal gradient,and superelevation gradient rate is also determined.From the perspective of conducive to pavement drainage,the superelevation transition method of multi-lane expressway is improved,and the drainage effect is verified.It is proved that the superelevation transition method combined using different superelevation transition gradient on transition curve and adding arch line can discharge the ponding of the superelevation transition section pavement to the maximum extent.Finally,according to the studied regression models,the design and improvement measures of superelevation transition section are proposed from two aspects: alignment condition design and pavement design.Considering the rainy visibility and water skiing,the calculation models of vehicle speed are established respectively,and the maximum safety speed limit values of different road longitudinal gradient and different rainfall intensity in rainy days are proposed.It is of great significance to promote the drainage of the superelevation transition section for the multi-lane expressway,improve the driving safety in rainy days,and ensure the quality of operation.