This paper is going to describe the design process of a simulator that assesses the costs of different means of transport. The evaluation not only will be done regarding the internal costs but also the external costs that will be translated to environmental costs, based on existing databases. The paper shows the development carried out to create this simulator and analyse all components of the logistical chain, i.e. port operation costs, road haulage costs and maritime leg costs. The simulation results have been validated with real data of actual maritime routes to check its reliability. As a conclusion, the costs simulator permits assess costs of new maritime trade routes comparing them with road transport.