Optimization Design Method Of The Length Of U-turn Lane On Urban Arterial Roads Based On Traffic Behavior

In recent years,the public security traffic administration department continues to explore and practice the concept of road innovation design.The design of traffic operation such as U-turn followed by right-turn and advance U-turn on urban arterial roads becomes common increasingly,the unsignalized median U-turn lane application also becomes more common accordingly.However,its length is mostly designed based on experience,without considering the traffic behavior rules of service object,and there is a lack of quantitative research also.Unreasonable Uturn lane length can easily lead to traffic conflicts,affecting the safety and efficiency of the road.Therefore,it is necessary to analyse U-turn traffic behavior and conduct research on the optimization design method of the length of U-turn lane on urban arterial roads based on this.Firstly,the analysis of U-turn traffic behavior was conducted.By analysing the concept of U-turn traffic behavior,this thesis focused on two typical types of U-turn traffic behavior: gap acceptance and lane selection.On the one hand,based on the characteristics of the scenario of multiple lanes on arterial roads,the behavior characteristic index of the lane selection rate of Uturn traffic was defined,and the lane selection rate and critical gap measurement methods matching the scenario of multiple lanes were proposed.And the behavior characteristics under the influence of factors such as vehicle type,lane width and opposing traffic volume were explored,providing a theoretical basis for the subsequent construction of the length design model.On the other hand,by analysing the influence of U-turn traffic behavior,the mechanism of the influence of U-turn traffic behavior on the space occupancy of U-turn lane was revealed,confirming the necessity of behavioral analysis on the design of U-turn lane length,and laying the foundation for the subsequent construction of length evaluation model.Secondly,the design model for the length of U-turn lane was constructed.The length of the U-turn lane was divided into three parts: broadening,deceleration and waiting.Among them,the waiting part was used to store the queuing U-turn vehicles.To solve the problem that the number of queuing vehicles was difficult to quantify,this thesis proposed a calculation method for the service rate of the U-turn queuing system and the total number of vehicles in the queue based on the analysis of U-turn traffic behavior characteristics,using the lane selection rate index as the intermediary and the knowledge of probability theory and queuing theory.Subsequently,referring to current standards and relevant research,specific calculation formulas for each part were proposed,and the length design model was constructed,serving the "calculation" phase of the optimization design method.Third,the evaluation model for the length of U-turn lane was constructed.This thesis developed a bi-level evaluation index system balancing both safety and efficiency by taking the impact of traffic behavior as the evaluation perspective;combined the subjective and objective weights which determined by using AHP and EWM respectively;used the TOPSIS to make optimal decision on the length design scheme.Then,the AHP-EWM-TOPSIS U-turn lane length evaluation model was constructed,serving the "evaluation" phase of the optimization design method.Finally,the four-phased optimization design method for the length of U-turn lane was proposed.This thesis proposed two design strategies for optimizing the length of U-turn lane based on the analysis of U-turn traffic behavior firstly,then proposed the four-phased optimization design method of "investigation,calculation,simulation,and evaluation",supported by the U-turn lane length design and evaluation models.The result of the case showed that the optimized length value can achieve better overall benefit,further verifying the scientific validity and effectiveness of the proposed method.This thesis studied the optimization design method of U-turn lane length from the perspective of traffic behavior,which not only can provide a methodological basis for the design of U-turn traffic operation of public security traffic administration department,but also further enhance the scientific,humanistic and refined level of design of traffic operation.