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.Applying the life cycle assessment methodology (according to the current ISO work undertaken for LCA), the system limits are defined so that the environmental aspects of the infrastructure are addressed from raw acquisition to final disposal. A complete road infrastructure LCA should therefore cover: the construction of the infrastructure, the operation of the infrastructure, the maintenance of the infrastructure, the recycling of the infrastructure. This study has not covered all the phases in details as this study focused mainly on the construction and operation phase of the infrastructure.The assessment of the use of the infrastructure, over its life time, mainly deals with the assessment of the impacts of traffic and therefore has required the choice of several assumptions and scenarios over the life time of the infrastructure: an estimation of the evolution of traffic flows, an estimation of the evolution of the breakdown of the vehicles according to their type (cars, lorry), an estimation of the evolution of the atmospheric gas emissions and energy consumption of the vehicles. Results concerning the traffic on the section (operation phase) are presented referring to the whole infrastructure life cycle and certainly gives a complementary view to vehicle life cycle analysis.Such approach is totally in line with the issue of sustainable development.