The introduction of 20mph speed zones in London has reduced road injuries by more than 40 per cent, according to a report published online in the British Medical Journal. Looking at statistics from 1986 to 2006, the report found the benefits of the 20 mph zones were most marked in young-child accident rates and the overall number of deaths and serious injuries.

Over the research period, casualties were reduced by 41 per cent, with deaths or serious injuries to children reduced by half.

Also, pedestrian injuries were reduced by just under a third and cycling casualties by 16.9 per cent.

Compiled by the London School of Hygiene and Tropical Medicine, the report estimated that 20 mph zones prevent 203 casualties a year.

The authors of the report supported the case for extending the zones in London, with the potential of preventing a further 692 casualties a year.

The authors found no evidence of "casualty migration" to areas bordering the 20 mph zones. In fact, in areas adjacent to the zones casualties also fell by an average of eight per cent

The authors said: "The additional effect of the 20mph zones was that of a step reduction in casualties and collisions. "This evidence supports the rationale for 20 mph zones not just in major cities in Britain but also in similar metropolitan areas elsewhere. Indeed, even within London, there is a case for extending the currently limited provision of such zones to other high-casualty roads."