Sir – Like The Oxford Times’ reporters, I find it very difficult to spot any motorists who are actually obeying the new 20mph speed limits.

This must be the greatest campaign of mass illegallity since the Suffragettes — though this time the law-breaking is mobilised in an entirely anti-social cause.

Motorists like to think that speeding is a victim-less crime, and the police — who of course themselves frequently enjoy travelling at high speed — too often seem to collude in this convenient delusion.

Government figures are very clear on this. Transport accidents are the most common cause of death among children (in 2000, 191 young people under 16 were killed on Britain’s roads) and the majority of those killed are not car passengers but kids walking and on bicycles.

Because the survival rate for those hit by cars is so much higher at 20mph than 30mph (a 95 per cent chance of survival for 20, versus little more than a 50:50 chance at 30), Oxford’s policy will undoubtedly save lives — but only if it is enforced.

People are rightly concerned about their children’s safety in other areas — no one gives a nod and a wink to paedophiles. But speeding motorists are ten times more likely to kill your child than a lurking stranger in a mac.

I think it is time the police gave us an answer. Will they start enforcing the law on speeding in 20mph zones? If not, how do they justify turning a blind eye to this widespread illegal and antisocial behaviour?

Next time a child is killed or injured on Oxford’s road by a speeding driver, it will not only be the motorist to blame — but also those authorities who neglected their duty to enforce this important and lifesaving new law.

Mark Lynas, Wolvercote