Greens demand 20mph speed limit

The measure, which would affect central London and residential areas where the limit is usually 30mph, is being demanded by the London Assembly Green Party, backed by road safety experts.

Jenny Jones, the Mayor's Green road safety adviser, said she had discussed the plan with Ken Livingstone and that he backs more 20mph zones, but needed a little "arm-twisting" to accept their introduction across London.

The Greens propose that 20mph would become the "default" limit on all London roads and councils would have to make a special case to exempt strategic routes such as bus routes and trunk roads. The limit would be enforced by new speed cameras.

At the same time, thousands of road humps, pinch-points and chicanes would be removed. Ms Jones said: "Making 20mph the normal speed limit would save lives and money and give a major boost to cyclists, who would feel safer."

Roger Geffen of cyclists' organisation CTC, said: "20mph makes sense not just for road safety; it also means cleaner air, less congestion and more people taking up cycling and walking. It would cut costs and bureaucracy enormously."

A study of 20mph zones in London found that they halved the number of people killed or seriously injured.