Rail Transit Network Generation Based On Urban Structure

As urban area expanding and urban population increasing,urban traffic problem is becoming more and more serious.Urban Rail Transit(URT)can effectively relieve traffic pressure of urban road system with low carbon emission.However,spatial and temporal imbalance of passenger flow and difficult transfer are stubborn problems in operation stage,which are mainly due to the fact that network design does not adapt to urban spatial structure.Considering the huge investment of construction and the huge cost of reconstruction,it is of great significance to accurately analyze urban spatial structure and design URT network meeting travel demand and urban development.By summarizing the current network design methods,it is found that the existing methods lack quantitative analysis so that the result is subjective and arbitrary.Therefore,in order to quantify the design process,a network generation method based on urban spatial structure is proposed.The urban population flow is used to reveal urban spatial structure and to calculate objective function of design model.Firstly,constraints of network design method are analyzed,including spatial constraints and efficiency constraints.For spatial constraints,the definition and significance of community detection are introduced,and then the advantage of Infomap algorithm is illustrated.Secondly,the adaptivity to road network and bus stations is explained.Finally,in order to obtain passenger flow distribution,this paper choose Logit distribution and the BPR function.As for network size and efficiency constraints,three main parameters,network density,network passenger flow intensity and network scale are estimated.Regression analysis,grey correlation analysis,entropy method is adopted for calculation.Then the generalized travel cost objective function is defined.Based on community detection result,the connections among clusters are generated.Then,the self-adaptive genetic algorithm is applied to get the alternative road set within clusters.Then,according to passenger flow,connections between clusters are generated.Finally,layout of network in then whole city level considering line design is obtained.Dial path search algorithm and Logit algorithm are used to get passenger flow distribution.Network integration and optimization model aims to balance the construction cost and passenger travel cost,so as to form a conceptual network planning result.Finally,taking city Z as case study,"inter-cluster network design — intra-cluster network design — network integration and optimization model" is applied to get network layout.Comparing the conceptual URT network with the actual URT network,the improvement of the network design method is proposed.Then,by comparing the conceptual URT network with the URT network applying network integration and optimization model,the necessity of community detection is illustrated.