Berlin (dpa) \- Cities around the world are turning to electric buses to cut engine emissions, but according to a new German start-up, the future belongs to hydrogen fuel-cell transit vehicles which are just as clean and can travel further. Arthur H2 Zero is the name of a new fuel-cell bus unveiled recently at the Bus2Bus trade show in Berlin. It has a range of 450 kilometres and uses only six kilos of hydrogen to travel 100 kilometres – making it more economical than any other fuel-cell bus on the market. It goes on sale this summer. Arthur uses a fuel-cell to generate electricity using a che…