Reducing the environmental impact of transport on Climate Change is an important policy target and the European Union has been spearheading legislation in this area. However, the EU has chosen, until now, to focus on tailpipe emissions, which only represent the impact of the use phase of the vehicle and leave aside the impacts of material production and car manufacturing as well as the end of life. Anyway, the corresponding regulations have given the direction for car manufacturer to focus on lightweighting, which is an important part of the solution. It is incomplete, however, as a more holistic approach encompassing all the phases of the Life of a vehicle ought to be taken on board, which is exactly what a Life Cycle Analysis (LCA) is meant to do.The purpose of this paper is to analyze the advantages and the limitations of LCA in the transport sector. Some very different categories of vehicles, in terms of powertrain, power and weight are examined as well as a degree of uncertainty in various LCA variables. The Greenhouse Gas Automotive Materials Comparison Model developed by the University of California Santa Barbara has been used to model these various vehicles.LCA demonstrates clear differences between many scenarios: the influence of the type of powertrain and of lightweighting - when carried out properly - are obvious. On the other hand, comparing lightweighting materials in terms of GHG emissions often exhibits differences which are less than the uncertainty of the data and thus are inconclusive. Lightweighting with Advanced HSS, however, is clearly a positive solution.