Modellering av slingor inom sjötransporter

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Disa Asplund
Jonas Westin

The Swedish national freight transport model system Samgods is a freight model that simulates logistics decision at a disaggregated firm-to-firm level. The model calculates total annual transport demand in Sweden for all transport modes based on a deterministic cost minimization approach. The model cannot consolidate commodities of different commodity types in the same vessel, train or truck and can only simulate vessels using direct routes between two ports. This implies that many of the features of sea transport such as utilizing larger vessels and building loops to consolidate goods from different ports is not possible in the current Samgods version. In this paper, we analyze the effect of removing restrictions in sea transportation especially by allowing the ship operators to construct and utilize loops. In the new model, LIFREM (Loops Including FREight Model), the shippers’ choice of sea transport routes is modelled as a mixed integer linear programming optimization problem. In doing so, we make use of a case study on sea transport of forest products from Northern Sweden to Western Europe. The results show that allowing predefined loops decreases total logistic cost by 10% and allowing the shipper to freely select loops decreases the cost by 21%. These results show that modelling of loops is important in order to realistically represent the attractiveness of the sea transport mode. This is also confirmed by the fact that the sea mode share increases by 2–4% in LIFREM when loops are allowed.

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