Integrated optimization of wagon flow routing and train formation plan

The integrated optimization of the wagon flow routing and train formation plan is provided. The problem is formulated as a mathematical programming model. The objective function aims at minimizing the train assembling time, train reclassification time, and trip time of the rail section. Some constraints indicate the reclassification capacity of stations, the number of classification tracks and the carrying capacity of rail sections. Furthermore, an improved bi-objective programming model is developed considering the reclassification workload balance of the technical stations. As an NP problem, using the traditional method to solve the model is complicated and inefficient. An improved heuristic with a greedy generation approach is proposed. Firstly, two greedy procedures are introduced to generate the initial integrated scheme. Then a matching and updating procedure is designed to solve the model. Finally, a real-life aggregated railroad network in China is given to evaluate the proposed model and heuristic. The experimental results show that the proposed heuristic is effective for solving the two models. The results solved by the bi-objective model can significantly balance the reclassification workload of technical station.