A Methodology for Assessing the Increasing Capacity Methods Using an Optimization Approach with a Case Study on Badrood- Ardakan Route

railway operators encountered lack of capacity. For improvement of capacity, the basic planning is required.The railway capacity is dependent on infrastructure, traffic, and operating parameters. The aim of this study is to present a methodology to investigate the appropriate solutions for increasing the capacity of railway bottlenecks. In this study, a new optimization model is presented based on multi commodity network flow model on a space-time network. The objective of the proposed model is to maximize the number of trains in the reference time. The inputs of the model are the characteristics of each train type, infrastructure attribute and network configuration. The most important constraints used in this model are related to the different kinds of the trains and number of the siding tracks at the nodes. By defining the proper criteria based on the capacity and the cost, operation of different proposed scenario for increasing the capacity is studied for that railway. We used the model to evaluate the solutions for increasing the capacity of Badrood-Ardakan railway as one of the Iranian rail bottlenecks. The results show that based on percentage of capacity index, the construction of two new nodes and two siding track between the two existing stations is the best option. Based on the cost of adding a train, the construction of two new nodes with a siding track between the two existing stations is the best choice. Finally, based on the cost –capacity index, building a new node (with a siding track) between the two existing stations is the best option