Research On The Influence Of U-Turn Upon Traffic Flow Downstream Signalized Intersection

In recent years, as the arising of the auto number and the limit of the roads, traffic problems in big cities have become more and more serious. In order to enhance transportation circulation efficiency, and to decrease traffic accidents and jams, measures are applied to resolve the traffic problems from aspects of perfect road network constructions, and to strengthen traffic management. Since the road network in big cities has become better constructed, scientific traffic planning, design and management seem to be more and more important.The existence of left-turn flow is an important reason to cause conflicts and traffic jams at intersections. Using right plus U-turn at down stream signal intersection as an alternative to direct left turns can significantly enhance efficiency and safety of the operation of relative traffic flows. Right turn plus U-turn has been implemented in foreign countries for many years, and the research on the influence upon the downstream signal intersection and efficiency of this project is plentiful. The research in foreign countries generally included the delay and travelling time model, but, foreign research was used to using data recursive methods to establish evaluation parameter (travel time, delay, etc.) models. A distinct character of recursive method is that it has a high precision for idiographic sites, but it is not in the ascendant on adaptability, as a result the study its conclusions are short of theoretical value.A prominent spirit of access management is flexibility, which means adjusting measures to local conditions. Most foreign research is based on local data, and there are a great deal of economic, social and cultural differences between China and foreign countries, so it is not appropriate to the copy the conclusions of foreign study to China directly. Recently, in China, U-turn has been put into practice at appropriate sites in many cities, and it certainly has acquired good effects. However, over all, the road governor find it untoward and non-objectivity to establish effective projects, especially for the orientation of U-turn sites , the accessorial establishment and the design are lack of theoretic guidance. In addition, because of the randomicity and the irreversibility of traffic phenomena, the design and improvement of right turn plus U-turn and the evaluation of its operational effects are lack of practical criterions.Lately, domestic scholars have committed themselves to study on right turn plus U-turn. Nevertheless, their work is localized on partial and microcosmic lays, instead of considering right turn plus U-turn as an alternative of prohibiting direct left turn as a holistic scheme and evaluating the operational effects systemically and comprehensively.As the reasons as above, the purpose of this paper is to study the operational process via theoretical analysis, and to set up theoretical models of direct left turn and right turn plus U-turn that can preferably reflect the relationship between travel time(delay)and road traffic conditions. These models are in order to incarnate the running mechanism and process of every interrelated traffic flows under right turn plus U-turn projects, so the methodology is applicable for right turn plus U-turn at any traffic flow and road conditions, giving this study a comparatively high theoretical value. Meanwhile, this paper also has studied the influence on the U-turn upon the downstream signal intersection and the whole research road based on the domestic traffic condition and VISSIM software.The dissertation is consisted of 6 chapters as follows:Chapter1 is the abstract part, the background of this study is recited, the conclusion of the past-time study is reviewed, the aim and the significance of the study are put forward, and the methodology and structure of the dissertation is briefly introduced.In Chapter2, the category of organizing the direct left turn vehicles including U-turn projects, gap acceptance theory and delay theory are briefly introduced, and will be helpful for getting the average waiting time to find a acceptable gap on artery on gap acceptance theory, delay at signalized intersections of right turn plus U-turn vehicles is also carefully studied based on delay theory.In Chapter3, the process of left turn and right turn plus U-turn from driveway to artery were carefully studied, the travel time and delay model of direct left turn and right turn plus U-turn vehicles were established based on gap acceptance theory. By comparing two models, we give the efficiency analysis under different traffic conditions.In Chapter4, influence on the U-turn upon the downstream signal intersection based on the domestic traffic condition was carefully studied, by using data recursive methods to establish evaluation parameter (saturation and adjusting parameter of U-turn) models.In Chapter5, the influence of right turn plus U-turn on the whole research road based on the VISSIM software was carefully studied, by comparing the non-U-turn and U-turn traffic management, the chapter give the comprehensive influence.Chapter6 is the sum-up part, in which the primary work, the final conclusion , the significance and the applied fields of this dissertation are briefly depicted, the subsequent work need to be accomplished is also conceived.Chapter3 to Chapter5 are the primary part of this dissertation.Chapter2 is the basis of Chapter3 to chapter5, which are the pivotal part of the study, in which the efficiency of right turn plus U-turn and the influence on the U-turn upon the downstream signal intersection and the whole research road based on the domestic traffic condition and VISSIM software are studied, being of help for the transportation agencies to manage left turns and crossing movements on multilane highways.