Most «business-as-usual scenarios» built up till now have shown that hydrocarbon resources scarcity and the growing release of greenhouse gases will bring the world far away from sustainability over the next decades. Then, deep changes in behaviours away from «BAU» are unavoidable long before the turn of the century in a move towards a post-carbon society. Urbanisation and mobility are probably the domains where these changes might be the most important and they will be necessarily driven and limited by socio-economic and cultural forces that will dominate the century. They will induce further deep changes in behaviours of consumers and producers and are likely to deeply impact the use and production of bulk materials, large energy consumers and GHG emitters. To address these challenges, key milestones were defined by the EU : - A 20% reduction (minimum) of CO2 emissions by 2020 (compared to 1990) in Europe - A reduction of the GHG emissions by 2050 and after, so as to limit the increase of the temperature due to climatic change within 2°C. In this framework, the PACT project objective is to provide strategic decision-support information to decision makers to achieve these milestones. It will focus on 3 themes : - What shape the energy demand, and how this should evolve towards post-carbon concept, from the infrastructures viewpoint, in relation to urbanisation and land-use schemes, and that of the life-styles and behaviours, in relation to the available technologies. - The question of urbanisation and land-use from the renewable energy perspective, including that of the systems. - The role of social forces, actors, stakeholders in the transition process. PACT will address these issues in two phases: first, by developing the necessary analytical and conceptual framework, second in attempting to quantify scenarios of post-carbon societies at EU and world level by 2050 and beyond, using enhanced versions of the VLEEM and POLES models.