A battery-driven bus, which is not only quiet and pollution-free but competitive with the conventional bus on cost and performance has been developed by a group of British companies. The prototype, fifty-passenger single-deck vehicle, is to go in operation in Manchester shortly, and discussions with the Department of the Environment are expected to lead to a further batch of twenty going into regular passenger service in Manchester within two year and possibly in other cities, including London. Unlike the small government-sponsored battery bus now undergoing trials in provincial cities, whose low speed and range effectively limits it to city-center operation, the new Silent Rider, with a range 40 miles between charges and a speed of 40 m. p. h. , will take its place with diesel buses for normal urban and sub urban services. Its capital cost is higher (about 20,000 pounds compared with 1500 pounds) but lower maintenance and fuel costs bring it down to fully competitive cost with the diesel bus over thirteen year without taking into account the environmental benefits. The Chloride battery group--which is developing it in partnership with SELN (South-East Lancashire and North-East Cheshire Passenger Transport Authority) is confident of a market potential of 400 vehicles a year by 1980. The prototype weighs 16 tons, of which the batteries and passengers account for each. It has a single set of batteries, which take three and a half hours to recharge, against the normal eight hours of passenger traffic. A larger , Mark II version is being designed with two sets of batteries which can be charged in under a minute. That will allow low-cost night charging and greater operational flexibility. What had been the main factor preventing the development of battery buses?