The CATRIN project aimed at producing qualified research with the ambition to support the European transport policy, specifically to assist in the implementation of transport pricing. The project has thus both a strong research element and an element of short-term policy relevance. While this latter element requires a certain degree of simplicity the project emphasize that simplicity has to be created from the understanding of complexity. We have the ambition to have our research published in international scientific journals. We have involved different disciplines and does not focus on one single cost allocation approach but acknowledge that different viewpoints need to be taken in different situations. The project also recognizes that cost allocation (or pricing principle) recommendations need to be given in a short-term and a long-term perspective. The former stresses immediate implementation with a degree of uncertainty. The project will in a long-term perspective outline how these uncertainties can be resolved to suite the European transport policy for the future. Finally, our policy focus also means that CATRIN stresses the importance of dialogue with infrastructure managers.