Sir – I think your correspondent (June 18) is exaggerating in claiming the hydrogen-fuelled car as ‘The future of motoring’.

The salient features of the car that contribute to its energy efficiency are its lightweight composite body and the choice of electric traction, not the use of hydrogen.

Why not use the electrical energy directly instead of wasting some in the electrolysis process used to produce the gas, and then more in the fuel cell that converts the hydrogen back to electricity? Hydrogen easily leaks, and forms explosive mixtures with air over a wide range of compositions, so carrying the large amount needed for a worthwhile range, under high pressure, is risky.

The alternative of carrying liquid hydrogen is unrealistic: large amounts of energy are required to liquefy it, and then to keep it liquid at just 20 degrees above absolute zero. And a distribution system for electricity already exists.

While a top speed of 50mph is adequate for much of today’s car use, it is unlikely to appeal to more than a small minority in the macho culture promoted by most car makers. Most importantly for Oxford, despite the car’s small size, the small numbers will make little difference to the traffic jams that dominate most of the main roads.

Let us congratulate the engineers on producing an interesting test vehicle that may contribute useful engineering data towards the development of a practical fuel cell.

And please could they use a proper scientific measure of its energy use, such as kilowatt-hours per 100 passenger miles, including the energy required to produce the hydrogen. Does it also convert three-quarters of its fuel into waste heat, like a normal car?

Dr Andrew M. Pritchard, North Hinksey