Research On Dynamic Optimization Method Of Empty Railcar Distribution Under The Condition Of Marketization

As an important part of railway technology plan,empty car distribution is one of the problems that attracts more and more attention in the railway industry,which plays a key role in improving the efficiency of railcar utilization,reducing transportation cost and improving freight service quality.In view of the new era under the condition of marketization that transportation market puts forward higher requirement to proper allocation,as well as the current railway planning system hindering the development of dynamic empty car distribution,from the perspective of dynamic empty car distribution,railway administration(or company)empty car distribution and the whole network empty car distribution are studied,in order to efficiently allocate vehicle resources,meet the time-efficient requirements of empty car distribution,and promote the dynamic development of empty car distribution.The main contents of this paper are as follows:(1)The modes of empty railcar distribution are studied.The current mode of empty car distribution in China is studied from the perspectives of the use of railway freight cars,the principle and method of empty car distribution,and the operating mode of empty car distribution.Then it analyzes the foreign typical empty car distribution modes and points out the enlightenment of foreign advanced experience to empty car distribution in China.Furthermore,the requirements of market operation for empty car distribution are clarified and the design ideas of method for empty car distribution are expounded.(2)The dynamic problem of railway administration(or company)empty car distribution is studied.Combined with our railway operating features,the dynamic optimization method of empty car distribution at the level of railway administration(or company)is studied.A time-space network with discrete period combined with train formation plan and train schedule is constructed.The empty car distribution problem in railway administration(or company)is abstracted from the multi-commodity network flow problem and a dynamic optimization model of empty car distribution based on timespace network is established.In order to minimize the total cost of empty car distribution,the model comprehensively considers the actual requirements of discharging empty cars,assigning empty cars and substitution of car types.The feasibility and effectiveness of the model are verified by an example.(3)The dynamic problem of empty railcar distribution in the whole network is studied.From the perspective of global optimization and on the basis of foreign research results,the dynamic mode of empty car distribution in the whole network under the condition of marketization is proposed to deal with time-varying empty car supply and demand conditions by the method of real-time adjustment of the scheme.Based on ArcRoute model,the generation model of multi-types of empty car distribution scheme considering car route was constructed,and a solution algorithm based on Lagrange relaxation is designed.Specifically,the model takes into account the actual route of empty cars and the marshalling stations,and introduces the time-efficient penalty cost of empty car distribution into the objective function.An example is designed to verify the validity of the model and algorithm.(4)Case study.Taking Beijing-Guangzhou railway,Beijing-Kowloon railway and the connected road network as the background,the empirical study is carried out to test the dynamic mode of empty car distribution in the whole network.From the perspective of time-efficient requirement and total cost of empty car distribution,the two schemes in static mode and dynamic mode are compared and analyzed.The results show that,compared with the static mode,the time penalty cost of the empty car distribution scheme in the dynamic mode is reduced by 10.9%,and the total distance of the empty cars is reduced by 4.3%,which further demonstrates the superiority of the dynamic empty car distribution.