Hydrogen vehicles are now commercially available to purchase (or in development) from automobile manufacturers such as Toyota , Hyundai , Honda  and Daimler . It is possible to add a fuel cell engine and hydrogen supply to existing petrol driven vehicles. Symbio FCell has performed retrofits of this kind to vans and aim to work with trucks, buses and construction vehicles in the near future . With regards to performance, fuelling time and range these vehicles are comparable to conventional petrol engines. However one major advantage is that they only produce water in the exhaust (and no carbon dioxide, nitrous oxides or other harmful gases). The implementation of these vehicles into the consumer market is necessary to help Europe meet the challenging targets for lowering carbon dioxide levels.