Hydrogen-fuelled cars are not reliant upon petrol or diesel, which potentially makes them safer. Hydrogen fuel can be produced from renewable sources, such as wind or solar power, and does not have the ordinary car’s dependency on burning fossil fuels. Since cars account for roughly a third of greenhouse gas emissions, these futuristic vehicles could form part of an effective strategy to combat global warming. This is an idealistic scenario and there are many barriers to be overcome first. The existing designs for hydrogen fuelled cars are extremely expensive. The National Research Association also estimates that £8 billion would be needed to set-up the refuelling stations required by hydrogen-fuelled cars. For a mass market product to be developed there needs to be increased cooperation between governments and industry to allow the infrastructure to lead the manufacture. In fact, hybrid and hybrid-electric car designs may prove to be a more worthwhile long-term investment for governments. Compared to ordinary cars, hybrids emit reduced levels of carbon dioxide, whereas hydrogen-fuelled cars emit only water and so are 100% clean.