This article is in line with the ideas and considerations of the PIARC Committee on the Environment (C14): In all phases of a transport infrastructure, from the initiating idea to its operation and replacement, the impacts on the environment have to be considered ". Only an approach based on life cycle analysis can provide a significant assessment to compare the various alternatives from the environmental point of view. The reference life cycle, for a railway track or a rnotorway, should exceed fifty years and should not necessarily be the same for each of the various stages of the project and its execution. The authors of this paper describe an evaluation rnethod in a very clear way. It is obvious that global and local impact analyses must be carried out However, such analyses represent a considerable amount of work. It will no doubt be worth studying the details of the implementation of the life cycle analysis in several real cases and identifying the significant values to be considered.