Multi-speed transmissions - manual or automatic - are only needed because of the inherent drawbacks of the internal combustion engine as a vehicle propulsion power source. There are other power sources which reduce or eliminate the needs for such transmissions, and these are likely to come into increasing prominence as the 21st century progresses, writes Jeff Daniels. (This article was extracted from just-auto's exclusive report: 'The global market for automotive transmissions: forecasts to 2010'.)