IT is interesting to read the AA's proposal to raise the speed limit to 80mph on motorways when suitable conditions exist ('Speed limit rise urged', May 9).

Research on speed limits indicates drivers tend to over-estimate the safe driving speed, thinking 60mph may be safe, for example, when conditions really merit 50 to 55mph. If the limit were increased to 80mph deaths could increase by about 20 to 40, plus extra injuries of about 1,000 a year.

The second major consideration would be extra pollution caused by higher driving speeds. The 70 to 80mph is a 14 per cent increase in speed but the pollution effect is much higher, on average a 45 per cent rise. The proposal would be harmful and should be rejected.

Colin Clarke,

The Crescent,

Stamford Bridge.

Updated: 10:22 Friday, May 13, 2005