Calculation And Optimization For The Conveying Capacity Utilization Of Urban Rail Transit

Owing to its great capacity,high efficiency and low unit energy consumption,urban rail transit system has become the first choice to overcome traffic congestion problems in some cities.In recent years,China has entered a rapid development period,and the disparity characteristics of passenger demand in space and time is continually increasing with expanding urban rail transit network scale.Because of the great construction investment of urban rail transit system,how to use the limited investment to optimize configuration under the premise of meeting passenger travel demand is an important task to operation management.There are two important targets of operation management,which is to improve the service level of urban rail transit and reduce business operating costs.To achieve these two targets,we need to deep understand the relationship of passenger demand and capacity supply in urban rail transit system.This paper will analyze the main factors influencing conveying capacity utilization,propose the calculation and evaluation method of conveying capacity utilization,and establish train operational scheme optimization model by considering the disparity characteristics of conveying capacity utilization in space and time.The main contents and conclusions of the dissertation are shown as follows.(1)Influencing factors of conveying capacity utilization,i.e.,the fixed equipment,mobile equipment,train operational scheme and passenger demand characteristics,are analyzed based on related literatures.Then the relationship among the factors and their influence on train capacity utilization is analyzed.The result indicates that the four kinds of factors influence the maximum conveying capacity,vehicle capacity,the actual scope of conveying capacity and train capacity utilization.Passenger satisfaction is directly related to load factor of the carriage.If the load factor is large than 0.65,passenger satisfaction drops sharply.(2)Based on the train capacity utilization,the calculation methods of conveying capacity utilization in section,line and network are proposed.The characteristic of the conveying capacity utilization in space and time of Beijing urban rail transit is analyzed in the mean level,disparity and fluctuation characteristic.Passenger comfort evaluation standards are divided by train capacity utilization.The ranges of conveying capacity utilization are divided by the relationship of the weighted average and standard deviation of conveying capacity utilization.The result indicates that affected by single routing mode,the characteristics of conveying capacity utilization are similar with the characteristics of passenger demand.The conveying capacity utilization differs significantly in space and time.The section conveying capacity utilizations in the central zone of the network are larger,which is about 40-50%,and the section conveying capacity utilization are smaller in surrounding regions of the network,which are mostly below 30%.The section conveying capacity utilizations in surrounding regions of the network are volatile widely.The equilibrium of line conveying capacity utilization is higher at noon and in the afternoon,but lower in the morning and evening rush hours.The conveying capacity utilization of circle line is balanced and service level is high.The service level of suburban line in morning rush hours is low.(3)By considering the disparity of line conveying capacity utilization in space,the optimization model of train operational schemes is established.The decision variables are the routing plan,the formation plan and service frequency.The optimizing goals are the line conveying capacity utilization maximization,the used train number minimization,and passenger travel cost minimization.The passenger waiting time,transfer times and crowded cost are calculated by considering group passenger demand.Based on the model characteristics,the algorithm combined with linear weighting method and genetic algorithm is designed.The applicability of the single routing,nested routing and joint routing is analyzed under different demand situations.The result indicates that multi-routing mode can effectively improve the line conveying capacity utilization and spatial equilibrium,and serves the common interests of both passengers and operators.Compared with single routing,the conveying capacity utilizations of nested routing and joint routing are increased by 19.55%and 23.70%respectively.The equilibrium of nested routing and joint routing are increased by 63.74%and 51.92%,enterprise indexes like the used train number and the used vehicle number are optimized by 11.29-19.17%,and passenger travel costs decrease by 14.58%and 14.63%.Taking line conveying capacity utilization maximization as an optimal object can better match passenger demand and reduce operating cost.Improving the target weight of line conveying capacity utilization makes for better overall operating efficiency.Multi-routing mode is suitable for one line of unimodal section passenger flow.Maintain the maximum passenger flow section position and value unchanged,and if the passenger demand in the unimodal sections is more than 30%,multi-routing modes are more suitable than single routing mode.(4)By considering the time-dependent passenger demand and the disparity of the section conveying capacity utilization,train operational scheme optimization model of nested routing mode is proposed.The optimizing goals are the minimization of the section conveying capacity utilization standard deviation,used train number,and passenger travel cost.The calculation method of train capacity utilization under time-dependent demand is proposed.The linear weighting method and genetic algorithm are used on the designed examples for validation.Combined with the example,the efficiencies of five train operational schemes are analyzed,and the effect of time-dependent demand to the equilibrium of section conveying capacity is analyzed.The result indicates that taking the equilibrium of section conveying capacity utilization as one of the optimal objects is better adapted to the time-dependent passenger demand.Compared with even train operational schemes,the section conveying capacity utilizations are optimized by 53.95-64.11%in the optimum train operational scheme.The maximal load factors are reduced by 13.31-18.5%.Compared with other uneven train operational schemes,the section conveying capacity utilization is optimized by 17.09%.The equilibrium of section conveying capacity utilization increases by 44.09%.The maximal load factor is reduced by 6.8%.This model can effectively reduce the maximum train passenger capacity utilization.The more uneven the passenger demand is,the better the optimization effect is.