Sir – P. Hawtin’s letter (January 29) about traffic calming is long on unsupported assertions but short on facts.

He throws about the phrases ‘mistaken’, ‘misapprehension’ and ‘wrong’ with gay abandon, but fails to prove any of them.

In particular, the idea that there is any sort of effective [speed] enforcement action by the police in Oxfordshire is absurd.

On the A44 Oxford airport to Cassington turn, a section of which I have many years’ experience, normally I am among a minority of drivers who observe the 50mph limit. The same goes for the A34 Botley to Hinksey section, where I am regularly overtaken by heavy goods vehicles (including articulated lorries) doing 60-70mph and by cars doing 70-80mph. There are no speed cameras on either section, nor any other attempt to enforce the limit.

Dr Hawtin offers no evidence for his categorical statement that the accident rate on Cowley Road has fallen because of county council investment in calming measures. Even his figure of £2m is a pure guess, as he himself admits. And taking at face value as he does, without any doubts whatsoever, the Government’s assertion that ‘introducing a 20mph speed limit generally reduces the average speed of vehicles by just 1mph’, strikes me as very naive. Since when have such Government figures been the gospel truth and to be accepted without a question? Of course speeds ‘scarcely change’ without enforcement. Until enforcement is introduced consistently, many drivers will continue to flout the limit.

This applies to 20mph as it does to 50mph. Whether the politicians and the police have the will to put such enforcement in place in addition to planting pretty red,white and black metal signs all over the shop, is a separate issue.

John Kinory, Steeple Aston