Research On Double-layer Route Guidance Strategy In Urban Road Networks Based On MFD

Route guidance is an important means and an effective way to alleviate the problem of urban traffic congestion.It can be divided into central route guidance and distributed route guidance.Central route guidance from the manager's point of view,regarded optimizing the system as the goal,in order to maximize the overall operational efficiency of the road network,complex calculations make it difficult to meet the realtime requirements of dynamic route guidance;Distributed route guidance from traveler's point of view,regarded optimizing the user as a criterion,in order to achieve the individual travel benefit maximization,however,a single path often lead to "crowded transfer" phenomenon.Therefore,this paper,combining the two,proposes a double-layer route guidance strategy.In the upper layer,it carries out the dynamic traffic assignment under the condition of system optimum to generate the travel sequence of the sub-regions.The lower layer searches for the path under the user optimum conditions.This strategy effectively compensates the lack of the two,which is a useful attempt to improve the traffic guidance system.MFD theory,as a mean of studying the macroscopic traffic characteristics of road network,through the research content of the whole paper,which provides a method to analyze and evaluate the operation level of road network and lay the foundation for the development and implementation of the double-layer route guidance strategy.The work of this paper is mainly reflected in:(1)Through the re-selection of variables,we construct a MFD model which expresses the relationship between the operation capacity of the road network and the number of running vehicles,and analyze the rationality and practical significance of the model,and introduce a way to acquire the MFD of urban road network.(2)A multi-step sub-region partitioning method is proposed through the principle and basis based on MFD.The partitioning method combines the static initial partition and the dynamic division,and uses the mean shift clustering algorithm and the hierarchical clustering algorithm to realize the partitioning process.(3)This paper proposes a double-layer route guidance strategy in an urban road network.It considers the willingness of both traffic managers and traffic travelers,and combines central route guidance and distributed route guidance.It is a compromise between system optimum and user optimum.In the upper layer,the dynamic flow evolution model of the sub-region is proposed based on the MFD,and the dynamic traffic assignment under the system optimum condition is proposed.In the lower layer,dynamic traffic assignment model under the user optimum condition is used to generate the detailed path.