A programme of building of 16 roads in England may be as much as £3.9 billion over budget, according to the Campaign for Better Transport (CBT).
It reports that figures obtained under the Freedom of Information Act show that some of the projects have cost 200% more than originally projected.
Said roads and climate campaigner Richard George: "We need to improve transport, but pouring money into this black hole isn't the way to do that."
He cites the fact that, overall, the 16 roads were 54% over budget. Among those open for traffic in 2008/09, the A14 Haughley New Street to Stowmarket scheme in Suffolk was 250% over, while the A38 Dobwalls bypass in Cornwall was 205.9% over.
Meanwhile, the CBT found that of 20 bypasses built, after one year 60% had more traffic than predicted on the new bypass as well as on the old, bypassed, route, while 40% had 25% more traffic on the old route.
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