Research On Bottleneck Identification And Capacity Enhancing In Urban Rail Transit Network

The networking will become main development trend in urban rail transit at major cities of China, with the constant development and perfection of urban rail transit, it has been operated from single line gradually to multi-line and evolved into network, and the transport service will be significantly improved. Rational layout of transfer station and efficient transfer facilities makes the passenger-attracting scope realized qualitative enhancement in urban rail transit network, passenger flow in related line will also be greatly increased. Especially the lines in the central areas of city, because the gathered transfer passenger flow of multiple lines, passenger flow in the peak period will beyond the actual capacity of lines, result in congestion, and make up the bottlenecks. In addition, due to the unreasonable plan of network, it will lead to the ascension of the network capacity subject to certain extents or station facilities and other areas. Under such circumstances, effective identification for the network bottlenecks, accurate positioning for the urgency degree, and the thorough research of these relief measures, will effectively promote continuous improvement and development of the urban rail transit network, and lay out the foundation for the realization of backbone function in urban public traffic.This paper regarded the demand sacrification of resident as object, focus on the thorough research of bottleneck identification and sorting method in the network, capacity strengthening measures of bottleneck, traffic organizations of multi-track segment, and put forward the theory method of network bottleneck identification and capacity enhancement in urban rail transit. The main research contents be composed of five aspects as listed below:Firstly, the bottleneck in urban rail transit was summarized considering the service features of bottleneck starting from the network. According to the network components, the four-level identification process and method of the static network bottleneck was built by using of the TOC; and after the division of dynamic bottleneck into capacity bottleneck and service bottleneck, the four-level identification process and method of the dynamic network bottleneck was also established considering the indicators of service level. The example explained the specific application of four-level identification method of dynamic capacity and service bottlenecks in the network.Secondly, targeted at the physical structure and capacity supply structure of network, the multi-attrribute error-eliminating sorting method was adopted to sort the urgent degrees of static network bottleneck via complex network statistic indicators which includes the capacity and demand betweenness, unit weight and weight distribution difference, etc; and the dynamic multi-attrribute error-eliminating method with uncertain-important attributes was construct considering the features of different stages in urban rail transit and by introducing time weight to sort the urgent degrees of dynamic capacity and service bottleneck.Thirdly, it researched the measures about capacity enhancement in bottlenecks from both the transportation organization method and equipment reconstruction. On the basis of system analysis about the concrete strengthening measures in transportation organization, the train schedule optimization models of skip-stop train based on the stop time optimization and express/local train based on the station classification were built from the point of balanced capacity and demand. Then, it summarized and described the measures such as system upgrade, signal transformation and station, line reconstruction which were feasible. And through the example, suitability and effectiveness of the capacity strengthening measures were analyzed.Fourthly, proceed from the aspects of all-stop and skip-stop, it respectively conduct systematical analysis for the rationality and its applicable condition about train operation organization modes in three-track and four-track zone. And the multi-attrribute error-eliminating sorting method was applied to conduct the decision-making of feasibility about the capacity strengthening measures considering the comprehensive decision attributes such as implementation difficulty, relief effect of capacity and service bottleneck, expression level of passenger demand, complexity of operation, enterprise cost and revenue.Fifthly, taken the express/local train opreration in four-track as object, and according to the analysis of influence relation between train routing schem and stop schedule plan, the bi-level programming model for comprehensive optimization was built based on the decision results of operation modes and the thought of comprehensive optimization. In this model, the upper level was aimed to get the smallest enterprise operating costs considering the constraint includes available number of emu, the maximum and minimum train headway, demand fulfillment and stopping requests; and the user equilibrium assignment problem which pursue the minimum generalized travel cost of all passengers was the lower level. Then, it designed the solving process via applying the paralleled genetic-annealing algorithm based on learning mechanism. Finally, the example shown the relief effect of express/local train opreration mode in four-track for the capacity and service bottleneck.