Research On The Traffic Organization Mode Of Roundabouts And The Technical Index Of Turbo Roundabout Intersection

Roundabouts(hereinafter referred to as roundabouts)are common types of urban level intersections,which have the functions of safety,beauty,environmental protection and traffic calming.However,the problem of traffic congestion in roundabouts is becoming more and more serious.At present,signal control is mostly used in our country,but traffic flow selflocking and traffic safety problems may occur.Therefore,on the basis of retaining the advantages of conventional roundabouts,foreign countries have proposed turbo roundabouts to improve traffic congestion and traffic safety and operation efficiency at intersections.First of all,the paper analyzes and summarizes the traffic organization modes of the roundabouts based on the movement characteristic of the roundabouts,and describes the traffic organization modes and characteristics of the new types of roundabouts: turbo roundabout,double roundabout interchange,teardrop roundabout,and other new types of roundabout.Through the analysis and comparison with the conventional roundabout,their respective advantages are clear.At the same time,the traffic organization and characteristics of turbo roundabout are deeply studied.Secondly,the layout and geometric structure of turbo roundabout are analyzed,and the minimum radius of the central island is obtained according to different layout types.According to the theory of vehicle lateral safety width,the calculation formulas of the ring width and entrance width are proposed,and the suggested values are given.According to the components of the cross section of the turbo roundabout,the calculation models of the cross section of the ring with different geometric structures are established.Based on the theory of vehicle driving stability and vehicle turning space,the proposed value of entrance and exit radius is proposed.Based on the movement characteristic and uniform transversal cosine lane change model,reasonable suggested values for the length of the entrance lane and the length of the transition sections are given.Finally,based on traffic flow theory and gap-acceptance theory,a basic turbo roundabout traffic capacity calculation model is established.Taking a roundabout as an example,the design scheme of turbo roundabout is obtained.VISSIM simulation software is used to evaluate the traffic efficiency and safety of turbo roundabout.The advantages of turbo roundabout are verified.The simulation analysis of conventional roundabout and turbo roundabout under different traffic saturation and steering ratios is carried out to further clarify the advantages of turbo roundabout.At the same time,the traffic safety setting of turbo roundabout is studied,and the recommended setting methods and requirements of traffic safety facilities are obtained.