There are reports that suggest that the addition of small quantities of hydrogen can improve the efficiency of the operation of a diesel engine and reduce the emission of particulates and perhaps even NOx. However, the published work is inconclusive and there is no systematic study available in the open literature. In this project we will perform a thorough study at the department of mechanical engineering at UCL in an effort to realize these benefits, optimize the engine efficiency and reduce emissions. In a separate project Cella Energy, the Motor Industry Research Association (MIRA) and Unipart are developing a safe solid-state hydrogen storage system as part of an existing TSB project. In ‘Co-Combustion’, once UCL have determined the optimum operating conditions, tests will be carried out using this system; first at UCL and then in a 2 litre diesel engine ‘mule’ vehicle at MIRA. The innovation is three-fold: Firstly, the deployment of a novel hydrogen storage syste; secondly, the scientific and technical study embarked upon will resolve many of the remaining questions underlying how hydrogen injection augments ICE diesel efficiency, and thirdly, a unique commercial opportunity to fast track the hydrogen economy - this resides in the critical decision to charge a penalty fee for those vehicles entering a low emission zone with non conforming emissions. Initially this technology will be used to reduce emissions from older diesel vehicles, but ultimately it is hoped that it will be incorporated into new vehicles to augment or partially replace the technology that is currently used to filter diesel engine exhausts, particularly in Low Emission Zones such as London.