Transport accounts for 26% of the United Kingdom's greenhouse gas emissions, and is a main source of deadly pollution in cities. New vehicles are now increasingly available that drastically reduce or eliminate pollution from the tail pipe. The Committee on Climate Change advises that 60% of new car sales should be ultra-low emission vehicles by 2030. Electric vehicles, which run on batteries charged from the grid or on hydrogen fuel cells, can dramatically reduce the emissions associated with transport, and improve health in cities. They can also act as a source of power storage and supply helping to balance the electricity grid.