Report from a European Commission working group on the feasibility of carrying out a full spatial and ecological assessment of the trans-European transport network (TEN). The study developed and tested a number of indicators to consider the availability of data and to identify issues for further research, if necessary. One of its main findings was that practical difficulties arise in an assessment of the network due to the poor quality and availability of data at EU level. This report on its work is intended to promote further discussion between all stakeholders on the issue of strategic environmental assessment (SEA) in relation to TENs.