Research On Dynamic Service Network Design Of Railway Express Freight Train Under Elastic Demand

With the transformation and upgrading of China's economic structure,the demand for express transportation is increasingly sensitive to the quality of transportation services.Express Freight Train is a freight product launched by the railway department to meet the demand of express transportation.Improving the quality of its transportation service is conducive to attracting potential sources of goods.High-level transportation service quality depends to a large extent on the design of its operation plan.Therefore,considering the relationship between the operation plan of express freight train and transportation demand,optimizing express freight train's operation plan under elastic demand is conducive to improving railway transportation revenue and expanding market share.The operation time of express freight train is relatively fixed.Considering the high sensitivity of express demand to the timeliness of transport services at present,the relation between the operation time and demand will be considered in the study of the operation plan of express trains,and the operation plan including the operation time of express trains will be generated.Based on this,the main research contents of this paper are as follows:(1)Analysis of the current situation of China's railway express freight transportation organization.This paper expounds the basic connotation and transportation organization process of railway express freight,and sums up the basic features of express freight.Secondly,it makes statistics on the current situation of China's freight transportation market and analyzes the reasons why railway freight transportation accounts for a relatively low proportion.Finally,the main products and characterristics of foreign express freight transportation are introduced.Based on the analysis of the form and current situation of China's express freight transportation organization,the shortcomings of China's express freight transportation organization are summarized.(2)The relationship between express freight train operation plan and express transportation demand is studied in detail.Firstly,according to the classification of goods in the railway freight,the demand for railway express transportation is classified and the characteristics of various demands are summarized.After that,it introduces the connotation of express freight train operation plan and analyzes the factors affecting express freight train operation.Then,on the basis of influencing factors of express transportation demand and the characteristics of various modes of transportation,the connotation and specific performance of elastic change of express transportation demand are analyzed.According to the elastic change of demand in transportation volume,an elastic demand function is established based on generalized cost and logit model.Finally,a virtual example is used to quantitatively analyze the mutual feed relationship between express freight train operation plan and express transportation demand.(3)The design model of express freight train dynamic service network under elastic demand is established.Firstly,the basic connotation of railway express freight train dynamic service network is elaborated.The design principles,design objectives and design contents of express freight train dynamic service network are analyzed.After that,considering the elastic demand constraint,demand satisfaction constraint,arc segment capacity constraint and intermediate node flow balance constraint,the design model of express freight train dynamic service network under the elastic demand is established with the maximum railway transportation revenue as the objective function.(4)According to the characteristics of the model,an improved discrete binary article swarm optimization algorithm is designed,and an example is given to verify the effectiveness of the model and algorithm.The design results under the elastic demand and under the fixed demand are solved respectively,and the specific effects of optimizing express freight train operation route,stop plan and operation time on the demand express transportation are analyzed.The results show that considering the influence of elastic demand in the design of dynamic service network can improve the transportation revenue of railway departments,expand market share and realize the volume transfer from other transportation modes.