20mph zones

20mph zones are springing up in odd residential areas at the moment and by all accounts more are on their way. They are being brought in to increase road safety, although teaching children the "green cross code" might be a simpler alternative.

The Standard report that "Cutting speed limits in London to 20mph could increase emissions of carbon dioxide by more than a tenth, the AA claimed today.

Slowing vehicles down makes engines work less efficiently, and the AA has calculated that even on free-flowing routes, fuel consumption in a petrol car going 20mph can be 5.8 miles per gallon worse than at 30mph.

This is enough to produce an extra quarter of a tonne of CO2 every quarter mile travelled. On congested roads the effect can be even more marked, especially with small-engined cars."