Study On Traffic Organization Of Displaced Left-turn At Urban Intersection With Heavy Load

With Chinese economy and the vehicle ownership increasing continuously,traffic demand of the masses has been expanding dramatically,and traffic stoppage has become a widespread trouble in cities.Although there are diversiform optimized measures such as channelization design,forbidden left,reverse variable lane and signal green wave coordination,due to multiple restrictions such as the special location,traffic conditions and road resources of some intersections,the solving effect of intersection,as the bottleneck of transportation,is still not ideal with applying comprehensively a variety of traditional traffic optimization methods.Relatively speaking,displaced left-turn(DLT)is a novel measure that can effectively remove the conflict of the heavy left flow and the straight traffic flow in the opposing direction at the primary intersection,which has great effect on moderating urban transportation congestion.The research object of the paper is urban intersection with heavy traffic flows.And the paper systematically elaborates the types,traits and suitable prerequisites of DLT,and then builds the DLT dedicated lane length calculation model based on the basic channelization design of intersection.Meanwhile a timing method based on signal coordination control is proposed.In addition,the DLT combination scheme is designed,and the scheme adaptability and scheme optimization are carried out.Furthermore,the intersection improvement index system is established with multiple indicators such as average vehicle delay rate and saturation at the intersection,and the fuzzy comprehensive evaluation(FCE)model is setted to evaluate the comprehensive optimization effect of DLT.The followings are staple contents:1.The basic theory of DLT.Firstly,the diverse displaced left-turn design types and its corresponding attributes are clearly defined,and the corresponding setting conditions are proposed simultaneously from road geometric,transportation safety and economic conditions and so on.Moreover,the DLT dedicated lane length calculation is proposed based on the basic traditional channelization design of the intersection.In addition,the signal coordination control design method is putted forward.2.DLT scheme design and optimization.Firstly,various DLT types are combined to design,and various DLT combination schemes suitable for different traffic conditions are obtained.Then,traffic state distinguishment of intersection,DLT adaptability analysis and its scheme optimization are put forward.3.DLT optimization effect evaluation modeling.In term of traffic efficiency,safety and environment,the average vehicle delay rate,saturation,congestion delay index and other indicators of the intersection are used to establish an evaluation indicator system for intersection optimization effect,with which the FCE model based on Hamming closeness is constructed to evaluate the overall optimization effect of DLT.4.Case application.Traffic investigation and problem analysis were conducted at the peak time of an intersection in Xi’an,and then the DLT lane design was carried out.What’s more,the DLT design schemes were proposed and the scheme optimization and simulation assessment were prosecuted.The results show that DLT has effect on relieving the serious traffic congestion.