CE was asked by the Dutch Ministry of Transport, Public Works and Water Management to provide input for the international project ‘Reforming trans-port taxes (2003)’. The aim of this project, funded by the European Conference of Ministers of Transport (ECMT) and the European Commission, is to improve understanding of the consequences of an ‘optimum’ transport pricing policy. In such a policy, users pay for the marginal infrastructure and other external costs they impose on society. To this end, the marginal costs of environmental damage, accidents and congestion were computed for road, rail and water transport in Great Britain, France, Germany, Finland and the Netherlands. The results show that: