Building new roads makes traffic worse, say campaigners
New roads in England not only fail to ease congestion and benefit local economies but worsen traffic, countryside campaigners warn.
Road-building also "obliterates" rural views and harms nature, the Campaign to Protect Rural England says.
Its study of 86 road schemes completed between 2002 and 2012 says the majority damaged the surrounding environment.
But Sir John Armitt, of the National Infrastructure Commission, said it was essential to increase road capacity.
The government will spend £1.2bn on building and maintaining roads in the next year, which it says will cut congestion and improve journey times while boosting businesses and jobs.
Ralph Smyth, head of infrastructure at the CPRE, said road-building projects led to a "depressing, self-perpetuating cycle of more and more roads".
Roads were not delivering the congestion relief promised, he told BBC Radio 4's Today programme. "They improve it for the first year or so, then traffic rapidly increases."
The CPRE's research drew on official evaluations of 86 road schemes, which Highways England carries out for road projects costing more than £10m.
It said 69 of these road schemes had had an "adverse impact" on the landscape, including obliterating views and destroying ancient woodland and mature hedgerows.
And each road project it looked at, excepting one, saw traffic grow "significantly faster" than other regional roads.
In addition, the CPRE examined 25 road schemes which the government promised would boost the local economy.
The CPRE said that in 15 of these cases there was only "thin and circumstantial to non-existent" evidence that this had happened.
By Roger Harrabin, BBC environment analyst
To a driver in a jam, a bypass or flyover looks an obvious solution. But for decades, traffic planners have known this is not as simple as it seems.
That is because it is well established that often the process of improving a bottleneck will lead to new bottlenecks either side of the old bottleneck - I have deliberately used the same word three times.
A government spokesman said he accepted new roads would bring more cars on to the road.
But he said improved roads would cut congestion overall and make journeys quicker, safer and more reliable.
The government had to keep improving the system to cope with demand, he added.
Critics want to turn the issue on its head. They say more investment in trains and buses will reduce the demand for roads.
In fact, in cities there is typically a principle that to speed up car journeys you improve public transport.
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Congestion becomes worse as new roads encourage people to drive and create new bottlenecks, the CPRE has claimed.
It said road schemes often led to new business and retail parks being built, which rely on cars and can draw consumers away from town centres.
"You cannot build your way out of congestion," said Mr Spiers, who has called on the government to make road-building a "last resort".
But the government believes greater road investment is essential to the economy, added Sir John, who is deputy chairman of the Infrastructure Commission.
"You're not going to get away from the need for a good road network," he told Today. "You have to keep up and continue to invest to improve."
He said England needed better road and rail links to remain economically competitive, "particularly in the years ahead post-Brexit".
Sir John added: "If you talk to people in the Midlands and the North... they will say they want an improved road network."