SIR - Teddy Wright is probably correct (T&A, January 4) to be cautious about the possibility of large numbers of cars driven by compressed air.

The key will be in finding a cheap source of electricity that does not produce carbon to compress the air, and being prepared for a lightweight simple construction that will be closer to a three wheeler than a luxury saloon.

The Indian company Tata promises to have such vehicles in production this year and it will be interesting to see how they turn out.

Keith Thomson, Heights Lane, Bradford