An Algorithm for Optimally Removing Network Bottlenecks to Justify the Electrification of the Railway Corridors, Case Study: Railway Corridor at North of Iran

Electrification is one of the appropriate solutions to increase the railway network capacity. However, use of this solution without provision of the sufficient capacity and required infrastructure through the whole of the network, may not acceptably increase the attracted railway demand. In such cases, the electrification project may be uneconomical. This research aims to propose an algorithm to identify which bottlenecks of the network must be removed, in order to justify the electrification of a specific railway corridor. We investigated the electrification of the railway corridor at north of Iran. This corridor has a substantial capability for absorption of the freight transportation demand. The railway freight demand related to all of the origin-destination pairs of Iranian railway network, along with the capacities of all block sections of the network are considered as inputs of the problem. for freight assignment in the railway network, FARS (Freight Assignment in Railway System) software was used. This Iranian software is developed by transportation research center of Isfahan University of Technology (IUT), in 2013. The assignment method used in this software is based on Incremental assignment. Different scenarios are considered and two main criteria are employed to compare the scenarios: tonnage of increase in railway freight demand, and economic index of benefit to cost called Net Present Value. According to the results, the electrification of the railway corridor at north of Iran, with no resolution of the bottlenecks in other locations of the network, cannot absorb a remarkable demand. The individual electrification of the mentioned corridor can only increase the absorbed freight demand from 1.65 million tons to 1.95 million tons, which is not considered an impressive progress. In this scenario, the Net Present Value (NPV) index and Net Uniform Annual (NUA) index are negative, which implies that the execution of this scenario is uneconomical. The low increase of the demand absorption is due to the existence of the capacity bottlenecks in other parts of the railway network. The existence of these bottlenecks prevents the complete usage of the added capacity potential emerged from the electrification. Consequently, the possibility of handling the transportation demand at north of Iran would be limited. By using the algorithm proposed in the present study, the main bottlenecks which prevent the load flow through the network, were identified. Then, by execution of the capacity increase scenarios for the identified bottlenecks, the absorption of the railway freight demand was increased to 3.97 million tons, with positive values for both NPV and NUA indices, which imply the economic justification of the railway electrification at north of Iran, simultaneously with improvements for capacity bottlenecks at other parts of the railway network. In other words, to achieve the absorption of the freight demand of the railway corridor in north part of Iran, it is not adequate to merely increase the capacity of this corridor itself. The railway electrification project in a specified part of the network is preferred to be performed simultaneously by the capacity improvement projects in other parts of the network. The proposed algorithm can be used in decision making for justifying the railway electrification projects.