Validering av sjötransporter i Samgodsmodellen: version 1.1

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Jonas Westin

The project analyzes how well sea transports are modelled in the Swedish national freight model system Samgods. This first report comprises a short description of Version 1.1 of the model including calibration, a comparison of model results and statistics in 2012 as well as sensitivity analyses to test how the model reacts to different types of interventions. The second report, VTI notat 31-2016 Modeling of loops in maritime transport Case Study of SCA's RoRo operations in the Baltic Sea, examines how big the problem is that Samgods does not model loops (vessels calling more than two ports during a trip).

The existing Samgods model is a deterministic cost-minimizing model. It consists of several partially interacting modules: a) base matrices that describe the demand for 32 commodities, b) the logistics model that contains submodules for the choice of consignment size, consolidation of shipments from different senders, choice of transport chains, treatment of empty transports etc. and c) the rail capacity management tools (RCM) addressing capacity constraints in the Swedish rail network.

The calibration of the model focuses on tonne-km and modal split in Sweden as well as different regional distributions of the tonnes transported, but the distribution over vessels types is not taken into account. Our analyses show that the model calculates about four times as many tonnes transported by container vessels than the statistics. We see a need to check if the input data used for the modelling of container transports (vs conventional transports) is realistic.

Throughput (loaded/unloaded tonnes goods) was calibrated for 14 coastal sections and twelve aggregated commodities. However, we believe that the throughput per port should be a calibration target. The distribution of the gods on the ports is crucial in analyses of investments in fairways, locks etc.

Furthermore, the distribution of the port calls vessel categories and -size classes was not a calibration target. We show that Samgods model overestimates the number of calls to all freight vessels with about 50 percent. The number of container vessel calls is about five times higher as in the Swedish Maritime Administration’s database. The number of roro-vessel calls is about two times as high. The conformity for the other vessels is very good.

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