The fate of a series of A47 dualling schemes now rests in the hands of judges after the Court of Appeal heard an environmental campaigner's bid to block the projects.
It is now likely to be months before judges decide whether the government broke the law or not when it gave the go-ahead to dualling between Blofield and North Burlingham and Easton to North Tuddenham, plus the revamp of Thickthorn junction.
A hearing on Tuesday was the latest stage in the legal fight which former Green city and county councillor Dr Andrew Boswell has been waging over decisions by transport secretaries over the key Norfolk road.
His crowd-funded case that the government had broken the law in its decision-making, because the cumulative carbon impacts for the three schemes had not been properly assessed, was dismissed by the High Court last year.
But he won the right to take the matter to the Court of Appeal - further adding to the tens of millions of pounds that his legal challenges have already added to the overall costs of the works - where his lawyers yesterday reiterated their argument.
David Wolfe KC, representing Dr Boswell, said there had been "a failure" by the government to comply with legal requirements under the Climate Change Act and the Planning Act.
He said: "What is not done, and this is the fatal step, is to compare the cumulative assessment with the national carbon budgets and then to factor that into the question of whether development consent should be granted."
READ MORE: Norfolk A47 legal battle backed by presenter Chris Packham
However, James Strachan, KC, representing the government, said it was wrong to suggest the secretary of state had "ducked" the issue.
He said the decision had been based on an assessment of the impact of all projects on a national, not local, scale and it would have been "irrational" to have done anything else.
He said: "The proper way to assess cumulative impacts is to look at the UK targets, because they incorporate all assessments from all sectors, which is much more robust."
The Court of Appeal decision from Lord Justice Jackson, Lord Justice Dingemans and Lord Justice Henderson, will determine whether work on the National Highways schemes, on hold because of the legal fight, can go ahead or not.
Chris Griffin, programme lead for National Highways in the east, said: "We stand by our plans and remain confident we can deliver significant improvements to both safety and congestion on the A47, as well as providing a huge boost to the regional economy."
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