The CATCH Project aims to develop a knowledge platform which will become a public information system for mobility related greenhouse gas (GHG) emissions reduction advice. The holistic Platform will provide travellers, businesses, planners and other mobility stakeholders with the tools to play their part in creating a new mobility culture promoting timely and informed climate-friendly travel choice and policies. The Platform will enable travellers to understand the climate change impacts of their choices, and take effective actions to reduce them, and enable policy decision makers to include carbon constraints into their actions. The Platform will include a range of CATCH tools, including a virtual environmental travel assistant, and be driven by the CATCH mobility knowledge engine. The main project activities to achieve this aim are: - Strong user understanding and user-based design; - review of the results in previous research, and engagement with existing EU funded projects WISETRIP and i-Travel projects, and the CIVITAS initiative; - realization of a database of GHG and transportation performance, which interfaces with appropriate emissions-related systems; - identification and assessment of climate-friendly travel scenarios; - development, testing and validation of the mobility knowledge engine; - defined exploitation path and wide dissemination of results through a dedicated internet web site, publications, conferences and workshops. CATCH will involve 40 cities and global carbon constraint professionals from mobility and related fields. Each city and professional has different experiences and brings new understanding. CATCHs expected results meet the following work programme objectives: - to guarantee at least neutral impacts on climate change; - to cover the critical gaps in existing emission information systems - to apply large scale demonstrations of integrated solutions for cities in Europe, regional and interregional mobility.