This document provides a methodical investigation of the main assessment steps that have led to the construction of Eurotunnel and it compares the results of the analyses that were achieved before the key decisions with the results of studies that have been undertaken since Eurotunnel is in operation. The analysis of successful and mismatched appraisals is followed by a series of methodological recommendations aimed at helping decision-makers to gain from positive experience and to avoid the pitfalls that Eurotunnel encountered. EVA-TREN is the acronym of “improved decision-aid methods and tools to support evaluation of investment for transport and energy networks in Europe”. It is a research aimed at improving decision support for large-scale transport and energy projects in the European Union. EVA-TREN is funded by the Directory General for Transport and Energy (DG TREN) of the European Commission, within the Sixth Research Framework Programme (FP6). EVA-TREN comprises, amongst other, the study of eleven significant investments in European transport and energy infrastructure. More information is available at: www.evatren.eu