Abstract
One of the main objectives for a rail company is to minimize the size of rail freight car fleet in order to reduce operating costs. The problem of rail freight car fleet composition is aimed at determining an optimal structure and size of freight car fleet in order to respond to actual transport demand. A rail company must have capabilities to respond to actual transport demand in case it wants to increase the level of competitiveness on the transport market. Therefore, it is necessary that the structure and size of rail freight car fleet correspond to the structure and size of rail transport demand. In this paper, we developed a two‐level approach to determining an optimal rail freight car fleet composition. This approach has been tested for the case of the Public Enterprise ‘Serbian Railways’ and the obtained results show the potential for a practical application of the proposed approach.
Highlights
We developed a two-level approach to determining an optimal rail freight car eet composition. is approach has been tested for the case of the Public Enterprise ‘Serbian Railways’ and the obtained results show the potential for a practical application of the proposed approach
Introduction e problem of rail freight car eet management belongs to a class of the most important railway optimization problems that are very complex due to the presence of various types and subtypes of freight cars, the size and value of rail freight car eet as well as because of its signi cant role in rail transport operations
Having rolling stock consisting of only one type of a rail car that can be used for transporting any kind of commodity is the most suitable choice made by a rail company. ese con icting requests must be solved by searching for an optimal composition of rail freight car eet satisfying demand and reducing costs (Bojovic 2002)
Summary
Papers appearing in literature dealing with the problem of vehicle eet composition can be classi ed into those discussing the problems of vehicle eet size where the type of vehicles are given and papers debating the problems of vehicle eet composition where decisions to be made relate to both the type of vehicles and the number of each type. Levy et al (1980) presented an integer programming formulation for the vehicle eet composition problem and developed several heuristics that are mainly based upon the concept of a ‘giant tour’ (a single tour linking the depot and all customers together). Ey developed a mixed-integer programming model that addresses long-term decisions concerning the number and type of vehicles that the company should operate. For each carious rail car type model, we can determine the minimum number of railcars needed to conduct the anticipated business. Sayarshad and Ghoseiri (2009) proposed a formulation and a solution procedure for optimizing eet size and freight car allocation wherein car demands and travel times are assumed to be deterministic and unmet demands are backordered. The best rail eet mix problem represents the rst level within the process of rail freight car eet composition. There is freight car eet though composed of cars but not corresponding to the structure of rail transport demand
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