Cutting speed limits to 20mph is increasingly popular. But campaigners warn this might not be the road-safety solution politicians say it is.
A report about support for 20mph speed limits in parts of our towns and cities has divided opinions sharply.
Last month, we wrote about a survey carried out by road-safety charity Brake and insurer Allianz.
Support for 20mph limit
It found that 80% of Brits said they were in favour of reduced speed limits in some urban areas.
This would include residential streets and near schools, for example.
This public support helps to explain why numerous local authorities around the UK have introduced 20mph limits in parts of towns and cities over recent years.
Councillors say that tighter restrictions on speed will lead to fewer road accidents, as well as an increase in the number of people encouraged to cycle or walk by safer roads.
But a number of campaigners are not convinced that 20mph limits can achieve these goals, or are the best way of doing so.
Eric Bridgstock is an engineer and independent researcher into road safety from St Albans.
He says that in fact there have been no reductions in casualties recorded as a result of cuts in the urban speed limit, once national trends and changes in traffic volumes have been taken into account.
What's more, Bridgstock believes there are a number of negative unintended consequences of 20mph limits.
"Pedestrians are lulled into feeling safer and are thus more likely to take less care, such as crossing the road without looking, often while using their phones," he says.
At the same time, lack of rigorous enforcement of the new limits means that traffic is moving at more or less the same speed as before, he adds.
Bridgstock thinks that the campaign group 20's Plenty has helped convince politicians that 20mph limits are effective.
"20's Plenty have a campaigning style that exploits the gullibility of the public," he says.
"Councillors want to be popular, so will often go along with it, but I have been contacted by some who see through the lies and deceit.
"The Department for Transport [DfT] have been infiltrated by a 'slower means safer' group, and appear to have lost their corporate knowledge of how to set appropriate speed limits to optimise for safety.
"They also seem to have swallowed the 20's Plenty propaganda."
Does slower equal safer?
However, a DfT spokesman says: "Research estimates that roughly one in 100 pedestrians are killed in vehicle collisions at 20mph, whereas around one in 15 are killed at 30mph.
"So clearly, lowering the speed limit on certain roads can save lives."
Statistics from Brighton and Hove Council, one of the authorities which has introduced 20mph zones, show that in the first six months of the scheme, traffic speeds fell on 74% of the roads affected.
There was also a "significant reduction" in the number and severity of collisions, the council said.
But Idris Francis, an engineer from Petersfield in Hampshire, says there needs to be more rigorous assessment of the evidence.
"What is really needed is detailed analysis of the existing schemes before any more are allowed," he says.
What do you think?
Are you for or against lower speed limits, and why?
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