Hydrogen fuel cell bus being driven in a bus garage in London,UK. This bus has been designed to reduce air pollution and noise by being powered by hydrogen. In the fuel cell, hydrogen combines with oxygen to form electrical energy. Water is produced as a by-product, forming a harmless vapour cloud as it leaves the exhaust. This bus can travel more than 125 miles before refuelling, making fuel cell buses twice as efficient as petrol or diesel engines. Hydrogen buses are being trialled on Route 25, which runs from Oxford Circus, W1, to Ilford, IG1. The British Government wants 600 low-carbon buses to come onto UK roads each year by 2012.