RA Mellen proposes a 20mph urban speed limit to curb what he calls motorists using the city's roads 'as their own private race track'.

Such a limit probably wouldn't deliver much safety benefit and would cause significant environmental damage.

At 20mph, most cars have to run in third gear at high revs, whereas at 30 they can run in fourth gear at a lower engine speed, thereby reducing fuel consumption, engine wear and Co2 emissions.

Irresponsible motorists are a problem which needs to be addressed - but so are cyclists and pedestrians who believe that the law doesn't apply to them.

Speed per se doesn't kill - the inappropriate use of speed does.

In many cases it would be perfectly safe to drive past a school at 50mph at 3am on a Saturday morning, but criminally irresponsible to reach 20 at 3pm the previous afternoon.

The infrastructure needed to operate variable speed limits everywhere would be too expensive, so a sensible compromise is to have fixed limits on most roads. In built-up areas, 30mph represents that compromise, though it should be enforced rigorously.

The system of fines for speeding offences should be replaced with short-term bans and repeat driving tests, backed up by mandatory jail terms for driving while disqualified.

Leo Enticknap,

Ingram House,

Bootham,

York.

Updated: 11:32 Monday, May 23, 2005