Methodology Of Network Layout And Optimization For Urban Rail Transit

With the acceleration of urban motorization,the problem of urban traffic is becoming increasingly prominent.The development of urban rail transit system has effectively relieved the traffic pressure of urban road system.But the construction of rail transit line is irreversible.Once the line is built,it is hard to change.Therefore,we should attach importance to the research of urban rail transit network layout optimization method,so as to give full play to the advantages of rail transit network.This paper first analyzes the basic form of urban rail transit network and the adaptability of each form,and then analyzes and calculates the topological characteristics of several network forms.On this basis,the important role of the three aspects of urban spatial circle division,urban road network and urban key passenger flow distribution point are analyzed respectively in the process of rail transit network layout,and quantifying the sub modules in the model.Then according to entropy weight theory,we put forward a method of calculating rail traffic network scale based on entropy coefficient method,and the results of each calculation method are given linear weighting,thus the final network result is obtained,and the error caused by the single calculation method is reduced.Then,this paper emphatically analyzes the optimization method of urban rail transit network layout,and constructs a network frame method based on multi-path search and traffic assignment.The network frame method based on multi path search ground on traffic district division of urban space.Construct the centroid point passenger flow gravitational model and the importance degree model of the centroid point.The hybrid optimization control model is established by two targets of maximum passenger flow gravity and the highest node importance,and the search process is completed through the F-W algorithm.Finally,the search process is completed.Put the space path into the planned urban road network.The network frame method of traffic assigned is based on traffic distract,and takes distance for constraint,then selects the predicted OD matrix.Establish generalized cost model for each travel mode,and OD is allocated to road network under the constraint of minimum generalized cost.After a number of loop distribution and iterations,the sections that finally screen a certain flow rate are displayed on the map to determine the main passenger flow corridor and determine the main skeleton of the rail network.On this basis,the results of the two network frame methods are integrated and optimized,and a bilayer optimization model is constructed with the total cost and the network node degree two targets.Through the comparison and selection of multi-objective optimization algorithm,we use the tolerance hierarchical sequence method to solve the model built in this paper.Finally,the structure of the rail transit network is carried out in Xi'an,the parameters in the related model are calibrated,and the basic rail network of Xi'an is obtained.Finally,the landing scheme of the rail transit network in Xi'an is obtained.