Research On Waiting Area And Signal Control Method Of Roundabout

In recent years,traffic congestion is becoming increasingly serious in China,and consequently more traffic problems such as “loop-block” have appeared at unsignalized roundabouts.Signal controls are adopted at some of the roundabouts to solve the problem,and have improved traffic capacity to a certain extent.However,there are still some limitations.The left-turn vehicle capacity of the common left-turn secondary control method is limited by the capacity of the left-turn storage area,and the vehicle delay is higher when the traffic volume is not high.However,through different release methods,the single-weight control method may cause serious traffic congestion,or make low utilization efficiency of the space resources at roundabouts.To sovle the problem,the author proposes to set up left-turn waiting area and straight waiting area at roundabouts,and separate traffic conflicts from each direction and improve the utilization rate of space resources at roundabouts by coordinating the traffic signals at the entrance of roundabouts.Firstly,common methods of signal control at roundabouts are introduced.Based on traffic simulation,the traffic and geometric conditions of the roundabout are defined,and problems of the left-turn single control method are analyzed to lay a foundation for the proposed method of traffic signal control at the waiting area of roundabouts.Secondly,basic ideas of setting up waiting area at roundabouts are introduced,and basic principles and processes of designing waiting areas at roundabouts are elaborated.Design processes are summarized as basic design,specific design and trajectory detection,and operation organizations of motor vehicle traffic flows as well as pedestrian and non-motor vehicle traffic flows are designed.Thirdly,the vehicle traffic flow conflicts at the roundabout with waiting area are analyzed,and then separated in time by phase design.The traffic flow operation states at roundabouts with waiting areas are divided into five categories,and delay models under five traffic conditions are established.Besides,the optimization model of signal control parameters with minimum delay as the optimization objective is constructed to analyze the influence of different traffic volumes,roundabout numbers and radius on the control efficiency of the proposed met hod.Finally,taking the roundabout of Xihe Road and Xinhua Road in Hailin City of Heilongjiang Province as an example,this study selects delay,throughput and average number of stops as evaluation indexes.On the basis of calibrating simulation parameters,the traffic signal control benefits of present situation and the improved roundabout are compared and analyzed by Vissim simulation,and verifies the effectiveness of setting waiting areas for roundabout.