Letter: Kyoto: just a start

Sir: Gavin Green (Motoring, 6 December) says people would be "amazed how clean a modern car's exhaust is". Many catalyst-equipped car drivers believe their fumes to be innocuous, but catalytic converters can never clean up all the by-products of internal combustion, principally the unburnt fuel and nitrogen oxides which interact to form ozone and smog.

Catalysts increase fuel consumption and do nothing positive at all on many typical short journeys. Drivers should recognise that the only effective way they can contribute to improving urban air quality is to leave the car at home.

IAN GARMAN

Cardiff