CleanER-D is a research project partly funded by the European Commission under the 7th Framework Programme. It aims to develop, improve and integrate emissions reduction technologies for diesel locomotives and rail vehicles.The project was launched to tackle the technical challenges inherent in complying with the new emissions regulations. The quantitative target of the project is to achieve emission levels within the limits established by the new European Directive 2004/26/EC and further upcoming regulations, while evaluating the best possible innovative and hybrid solutions for a contribution to the reduction of CO2 emissions.The 26 consortium partners from all over Europe will work in a strong collaboration to reach the goal of greening diesel vehicles.