SIR – In reply to Keith Thomson’s letter (T&A, April 14), I can inform him that I find it difficult to walk 100 metres, let alone run that distance.

In my school days, I did cross-country runs and I would not have chosen to walk them and I suppose I did exhale more CO2, but for a shorter time.

I stick to my argument about car speeds.

Philip Bird, Nab Wood Terrace, Shipley