I have seen and driven lots of cars of the future but none as comprehensively forward-looking as Hy-wire, a prototype that combines all General Motors's technologies of tomorrow. A luxurious four-seat saloon, Hy-wire appears not to have an engine: there is nothing in front of the driver's feet except an extra window to aid parking. It is driven by an electric motor powered by a fuel cell that creates electricity by combining on-board hydrogen with oxygen from the air. The complete drive system is hidden under the floor, contained within an aluminium chassis just 11in thick that GM boffins call the "skateboard".

Hy-wire requires you to learn to drive all over again. Instead of pedals and a steering wheel there is a control column, rather like that of an aircraft, which can be positioned to the right or left side of the car. Steering is by two handgrips — 20 degrees of movement produces full lock — that you twist to accelerate and squeeze to brake. These "drive-by-wire" controls have no mechanical connection to the wheels.

Driving the Hy-wire requires so much concentration that you forget about its revolutionary power unit. General Motors has a fleet of Zafira MPVs with the same fuel cell system that will do 100mph and run reliably and quietly with no pollution; the only thing that comes out of the exhaust pipe is water vapour. These prototypes cost millions of dollars but GM expects to have fuel cell vehicles on sale before the end of the decade, when the price will fall to the level of conventional cars and hydrogen fuel will be more widely available.