Research On Adaptability Between Capacity Supply And Demand In Railway Freight Network

ABSTRACT:Railway transportation which has obvious advantage in resource saving, environment protection and reducing cost plays an important part in the development of economy and society. In the face of this situation, effective measures to coordinate the capacity supply and demand are needed. The study on the adaptability between railway network capacity supply and traffic demand requirement has a positive and significant influence on the improvement of railway transportation management theory and would provide useful information on network planning.The law and theory of railway network capacity supply and demand are studied, and a systemic theoretical framework and an analysis method from macroscopic view is put forward for the first time, including the notation of network capacity and traffic demand, the framework of adaptability analyze, the optimize assignment of car flow, the estimation method of the maximum amount of freight the network can accommodate and the evaluation method of railway network capacity adaptability based on the models explored. The main contents and related conclusions are listed as follows:(1) The academic definition of supply and demand adaptability of railway network capacity is consummated by analyzing the notation of network capacity and traffic demand, which enrich the theory of railway network capacity utilization. According to the principles of static&dynamic, short&long term and microcosmic¯ocosmic analysis, a more complete railway network capacity adaptability study framework including supply and demand total amount adaptability, distribute structure adaptability, service quality adaptability and capacity flexibility is put forward. And indexes are proposed to measure the adaptability.(2) The analysis and evaluation method of supply and demand total amount adaptability and service quality adaptability, and especially emphasis is put on the study of railway car flow assignment method. Since the amount and distribution of empty car flows, which occupy the network capacity as well, lies on the freight flow distribution. A railway freight and empty car flow assignment model is built which combines the advantages of the multi-commodity freight flow assignment model and empty car flow assignment model proposed in this paper. Due to the character of railway transportation management, the constraint that the fright transportation between the same OD pair would choose only one path is included into the model to make the result more realistic. With this model, the composing arcs of the optimized transport path can be gained easily. With the optimize result, such as the volume and capacity utilization rate of arcs, the amount of freight can be transported within the capacity limit, the path offered and transport distance of each OD, so the adaptability indexes can be computed.(3) The analysis and evaluation method of supply and demand distribute structure adaptability and capacity flexibility is presented. A railway network capacity model under is built to estimate the maximum output of the network. Because the model follows the reasonable transport cost, freight and empty car flow relationship, the demand increase bound and one OD one path principles, so it can estimate the network capacity more effectively. The optimizing result not only shows the capacity of the network, but also shows the maximum capacity of each origin and destination. And these data are the basic parameters to calculate the distribute structure adaptability and capacity flexibility.(4) Since the adaptability evaluation system of railway network capacity supply and demand consists of four aspects and many indexes, AHP-grey fuzzy evaluation method is used to estimate the adaptability. Finally, a numerical example is given to prove the rationality and validity of the models and the evaluate method proposed.Above all, With the theoretic adaptability analysis framework and evaluation method presented in this paper, not only the status of the railway network transport capacity supply and demand adaptability can be evaluated from the macroscopic and microscopic view, but also the problems existed can be find out. And this would provide important reference for reasonable network planning strategies and decision making.