Dynamic Binary Mathematical Programming for Optimizing Freight Wagons Sizing, Case Study: The Railways of Islamic Republic of Iran

Document Type : Research Paper


1 School of Railway Engineering, Iran University of Science and Technology, Tehran, Iran.

2 Civil and Environmental Engineering Department, Tarbiat Modares University, Tehran, Iran.

3 Industrial Engineering Department, University of Tehran, Tehran, Iran.

4 School of Civil Engineering University of Queensland, Australia, Sydney.


transportation planners have always paid special attention to rail transport and its development due to its high capacity and low shipping costs. Two solutions apply to the development of rail transit 1. deployment of new infrastructure and 2. improvement of existing conditions and procedures. This study proposes a dynamic binary mathematical programming model to formulate the existing rail freight procedures. Also, the current study proposes two simulation scenarios (First Come First Served and Shortest Processing Time) for solving mathematical programming. Two different perspectives are considered 1. maximize the railway of the Islamic Republic of Iran (RAI) revenue and 2. maximize the rail transport companies' benefit. The main constraints are the loading /unloading capacity of stations, rail line capacity, and the capacity of locomotives to make up trains. Also, this study assumes that freight demand, travel time, and unloading /loading time are stochastic variables. In summary, this paper argued that the SPT strategy requires fewer wagons than FCFS, while the average productivity in SPT mode increases approximately by one unit, and unmet demand decreases. The results also show that the revenue of the rail freight companies in SPT strategy is more than FCFS strategy in all scenarios. Comparing the results of the models with/without taking wagons maintenance into account shows that if the maintenance of wagons is considered, the numbers of required wagons will increase, productivity will decrease, average revenue per wagon of RAI and the average profit of rail freight transport companies will reduce.


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