Research On Calculation Method Of Railway Network Freight Transport Capacity

The large-scale railway construction and market-based reform are promoted step by step with the changes of the economic and social development in China. The scientific estimating of the freight transport capacity of railway network is of great significance to the planning, reconstruction and use of railway network. Railway network system is a transport system which is composed of stations and lines. When calculating the capacity of network transportation, the actual characteristics of the traffic organization and the coordination of point and line capacity should be taken into account. However, train formation plan is seldom considered in the existing methods for network capacity, thus making the calculation result inaccurate. Based on this, a new method is promoted to calculate the carrying capacity of railroad network, which considers train formation plan and K-shortest path together. And stable bulk goods is taken as the research object. The main researches can be summed up as follows:(1) On the basis of summarizing the concepts of freight transport capacity of railway network, a new concept of network capacity is put forward. Then the influencing factors and characteristics of railway freight network capacity are analyzed.(2) By analyzing the typical models of freight transport capacity calculation and freight train formation plan for railway network, a new method which combines K-shortest path and train formation plan is proposed to calculate the transport capacity of railway network, i.e., choosing one path from the K shortest paths as the wagon flow path for the direct flows.(3) A mathematical model for railway freight network capacity is formulated, which has an integrative consideration on K-shortest path and train formation plan. Freight transport demand is allowed not to be satisfied. And two optimization objectives are considered, among which maximizing the total freight volume is the main objective and minimizing the total transportation cost is in second place. The linear weighting method is used to transform the multi-objective programming problem into the single-objective programming problem.(4) The Yen algorithm is used to solve the K shortest paths of each wagon flow, and a tabu search algorithm is designed to solve the model. Based on the simple railway network composed of 6 technical stations, a small-scale example is given. Then the model is solved by LINGO software and tabu search algorithm. By comparing the optimization results, the correctness of the model is verified, and the proposed algorithm is efficient in performance.(5) A railway network in Northeast China is selected as example network, which contains 19 technical stations. The model is solved by the proposed algorithm. It takes acceptable time to stop the iterations. The algorithm is verified to have evident practicability.