Research On The Design And Capacity Of Urban Cross-turbine Roundabouts

The successful application of turbo-roundabouts in foreign countries provides a new idea to solve the traffic problems at urban roundabouts in China.However,there are big differences between domestic and foreign traffic condition in urban road because of the mixed traffic conditions in China,our country can not appl y the foreign turbo-roundabouts to urban roads directly.Therefore,in order to apply the turbo-roundabout to the urban roads in China,the characteristics of mixed traffic flow at urban roundabout with four-leg is studied.On the basis of the above studies,this paper makes an intensive study of the design method and capacity model of urban turbo-roundabouts with four-leg under mixed traffic flow conditions in China.The traffic flow opreating characteristics of urban roundabout with four-leg is studied by combining field investigation,theoretical analysis and regression analysis: The following issues were researched : the characteristics of traffic flow rate,direction and compositions of motor vehicles at urban roundabout with four-leg;the characteristics of traffic flow rate an d compositions of pedestrians and non-motor vehicles at urban roundabout with four-leg;the speed characteristics of motor vehicles,pedestrians and non-motor vehicles at urban roundabout with four-leg.the traffic characteristics of pedestrians and non-motor vehicles are summarized at urban roundabout with four-leg.The distribution of ring flows time headways is verified that follows M3 distribution by hypothesis testing.The relationship is established between the ring flows and the free-flow ratio of urban roundabout with four-leg by regression analysis.The design of urban turbor-oundabout with four-leg is studied by combining literature research,theoretical analysis and software design : The basic characteristics and applicable conditions of the turbo-roundabout is summarized.Based on the characteristics of traffic flow at urban roundabout with four-leg in China,the design principles of urban turbo-roundabout with four-leg are summarized.Combining the design principles of urban turbo-roundabout with the code for design of urban road intersection in China,a design process of urban turbo-roundabout with four-leg is proposed.Based on the design process of urban turbo-roundabout with four-leg,the design method of each design element is studied and the completed traffic design method of urban turbo-roundabout with four-leg is got under the mixed traffic flow.The capacity of urban turbo-roundabout with four-leg is studied by combining literature research,theoretical analysis and regression analysis : Let the equivalent people groups describe the traffic flow consisted of pedestrians and non-motor vehicles,the conversion coefficient among electric vehicles,bicycles and pedestrians at urban roundabouts with four-leg is 1:1.53:1.61 that got by applying the method of time-space resources occupancy.The relationship is established between the quivalents people numbers and group nunbers by regression analysis.Studying the distribution of quivalent people group time headways,the distribution of quivalent people group time headways is verified that follows negative exponential distribution by hypothesis testing.Let M3 distribution describe the ring flows time headways of urban turbo-roundabout with four-leg.Let the equivalent people groups and ring traffic flows be independent priority traffic flows,the traffic conflict characteristics of urban turbo-roundabout with four-leg is studied under the mixed traffic flow at the entrance.On the basis of the above studies,the capacity model of urban turbo-roundabout with four-leg is established by applying the gap-acceptance theory.Applying the above research results to a practical case,the design scheme of urban turbo-roundabout with four-leg is obtained at the intersection of Guomao Road and Haiming Road.This paper makes comparison and analysis the traffic effiency of turbo-roundabout and normal roundabout by applying Vissim.The results show that the turbo-roundabout can effectively reduce the average delay and average stops of the vehicle that compare with the normal roundabout.Applying the above capacity model,this paper obtain the capacity and service level of each entrance of the design scheme of urban turbo-roundabouts with four-leg of Guomao Road and Haiming Road.This paper makes comparison and analys is the capacity and service level of turbo-roundabout and normal roundabout,The results show that the the capacity and saturation of each entrance of the design scheme of urban turbo-roundabouts in the main direction are better than those of normal roundabout;the capacity and saturation of each entrance of the design scheme of urban turbo-roundabouts in the secondary direction are lower than those of normal roundabout,but their service levels are is at the same level.