I was amazed at the content of Adam Trimingham's argument for speed reduction "across the board" (The Argus, December 28).

Perhaps he would have been better prepared to write the article had he previously reviewed published statistical data by the Department for Transport and others regarding speed and accident causation.

A good starting point could be the DfT's "Review of the Contributory Factors System", dated February 2004, which examines the factors in vehicle accidents.

Section B.2 tabulates analysed data provided by 13 police forces for 2001 and covers 60,979 accidents.

Excessive speed is not cited as a precipitating cause in any case - although it may be inherent in other categories (such as "loss of control"); as a contributory factor it is cited in 12.5 per cent of cases. Compare this with the precipitating factor in 10.6 per cent of accidents being "Pedestrian entered carriageway without due care (driver/rider not to blame)".

Bear in mind, also, that "excessive speed" embraces both "speed greater than the posted limit" and "inappropriate speed for the conditions". Figures from the Avon and Somerset police indicate 70 per cent of these "excessive speed" accidents occur within the legal speed limit.

With the suggestion of lowering speed limits generally, I quote from another DfT publication: "The 70mph and 30mph limits are well established and well understood and there is no case for a blanket change on safety or environmental grounds."

Around schools, a 20mph limit is not unreasonable - but most reasonable drivers would vary their speed to suit the hazard in any case. However, there is only a danger to children when they are going into or out of the school - is there a case for the lower limit to operate 24/7?

And what of the argument that lower limits would relax drivers' concentration, thereby raising the potential for more accidents?

Perhaps there are arguments to support variable speed limits as the hazards - times of day, weather conditions etc - vary. But competent drivers take note of these changing hazards and vary their speed accordingly.

-Leslie Paine, Crawley