Research On Key Technologies Of The Dynamic Route Optimization

With the increasing development of society and economy, the trafficcongestion is gradually becoming one of the most serious social problems currently.An important characteristic of the traffic congestion is randomness, which impliesthat it is unreasonable for travelers to make routing decisions totally depending ontheir previous traveling experience because relying on such experience will notonly result in some loss to individuals but also to deteriorate the whole trafficcondition. One of the most effective solutions to this problem is to establish theadvanced traffic guidance systems, providing the real time traffic information in theroad network by employing the routing optimization technologies to help thepre-trip or/ and en-route travelers make the right routing decisions.The most valuable function of the traffic guidance systems is to redistributethe traffic volume when it is not in equilibrium or the traffic congestion occurs insome part of the road network. Its ultimate goal is to maximize the efficiency ofroads and network and to minimize the travel cost of travelers. However, the statictraffic guidance systems based on the static traffic information can't be satisfying.Neither can the static traffic guidance systems identify the real time state of thetraffic condition in the road network nor recommend the optimal alternative routeto travelers to avoid such spots where incident happens or the congested segments.Obviously, the route recommended by the static traffic guidance systems is not thereal optimal one. If user follows such routes, he or she may be guided onto theseriously congested links and waste much time. Even worse, such case will degradeuser's trust in the traffic guidance systems, which has bad impacts on theapplication and promotion of the traffic guidance systems. Fortunately, the dynamictraffic guidance systems, based on the dynamic route optimization technologies,can totally overcome the shortcomings mentioned above. Therefore, the thesisfocuses on the key technologies of the dynamic route optimization.Stemming from the project key theories and technologies of the emergencymonitoring system on intelligent highways ,funded by National Natural Science ofChina under grant 50178025, and the project key theories and simulationtechnologies of dynamic traffic management and control in urban road network,funded by National Natural Science of China under grant 50338030, the thesisemphatically investigates the key issues of different stages during theimplementation of the traffic guidance systems. Taking account of their theoreticalsignificance and value in practice, the thesis first analyzes the route guidanceinformation demand of users and evaluates its value;then improves the datastructure to efficiently store the information relevant to the traffic guidance systems.Based on it, proposes an efficient dynamic route optimization algorithm;finally,pays attention to the congestion shifting problem triggered by the inappropriateguidance and the methods to prevent it.The thesis comprises of 6 chapters and their contents are as follows:Chapter One: Introduction. First, explain what and why to be investigated inthe thesis. Point out the thesis's value both from the perspective of theory andpractice, and then summarize the key technologies of the route optimization byintroducing the history and status quo of the route optimization technologies. Afterthat, the main content and structure of the thesis is given.Chapter Two: Analysis of the route guidance information demand andevaluation of its value. This chapter takes drivers in Changchun City as an exampleand analyzes drivers' demand on the route guidance information and theircomments on the value of the route guidance information currently available inChangchun City, some conclusions are obtained based on the data from the surveyconducted in Changchun City;at the same time, VISSIM is employed to furtherevaluate the value of the route guidance information.Chapter Three: Representation of Road Network. The principles to producethe electronic map special for vehicle guidance are proposed and the generalmethods to represent the road network are introduced in this chapter;then improvethe data structure to store the guidance information based on the previousachievements.Chapter Four: improvement and testing of the dynamic route optimizationalgorithms. First, introduce the classical routing algorithms and point out theirmerits and faults;then implement Dijkstra, A* and D* Lite using the computerlanguage VISUAL BASIC 6.0;finally, a novel algorithm is proposed and tested.Chapter Five: investigation on the congestion shifting problem. First, the rootcauses of the congestion shifting problem are analyzed and summarized;thendifferent methods to prevent the problem are proposed;finally, these methods aresimulated in part of one real urban road network and their performance arecompared.Chapter Six: Conclusions and the future work. The thesis is summed up andthe research process and the main contents of the thesis are looked back. At thesame time, point out the innovation and the existing problems, as well as theproblems that need to further study in the future.