Assessing the impacts of road infrastructures has always been an environmental, social and economical concern over the last decades, but assessing global impacts over the whole life time of the infrastructure (i.e. considering the traffic emissions over the life time of the infrastructure) has rarely been performed. With the help of the life cycle approach, such a global environmental assessment has been undertaken by the authors ( Pereira, Blanc, Coste, 1996 ). This paper presents the methodological approach, based on Life Cycle Assessment (LCA) and its application to the choice of a highway section among three alternatives.