High Court dates have been set for the legal challenge over whether multi-million-pound dualling schemes on the A47 in Norfolk should be allowed to go ahead.
The fate of three schemes - a revamp of the Thickthorn roundabout on the edge of Norwich, plus the dualling of stretches of the road from Blofield to North Burlingham and from Easton to North Tuddenham - will be determined by the decision of the court.
The schemes were all given the go-ahead by the secretary of state last year after recommendations by planning inspectors, following months of public hearings.
But climate change activist Dr Andrew Boswell, a former Green councillor on Norwich City Council and Norfolk County Council, launched a legal challenge, claiming the decisions were unlawful.
He argued the impact of carbon emissions which would result from the schemes had not been properly addressed, with the cumulative effect of all the schemes not considered.
He also argues the licensing relating to the Norfolk super-colony of barbastelle bats near the North Tuddenham scheme was not done correctly.
His application for what is known as a judicial review was accepted and it has now been announced the hearings will be held at the Royal Courts of Justice in London on Wednesday, May 10 and Thursday, May 11.
Judges will consider the evidence to decide whether the decisions to approve the schemes were lawful or not.
The challenge has meant National Highways has stalled the start of work on the schemes, while the ultimate decision of the court could yet prevent the projects happening at all.
Glen Owen, senior project manager for National Highways' regional investment programme in the East, said: "We continue to work with the Department for Transport ahead of the hearing, and remain committed to delivering these important projects, which have been specifically designed to increase safety and help to reduce congestion on the A47."
Dr Boswell, who has raised almost £30,000 for his legal fees through a crowdfunding campaign, said he was looking forward to the opportunity to present his evidence in court.
He said: "I think there will be quite a presence at the High Court from local people and nationally too.
"This case is at the forefront of challenging the government over climate inaction."
What are the schemes?
The A47 schemes were originally announced in 2014, by then prime minister David Cameron.
There was £300m earmarked for Norfolk schemes, along with other improvements in Cambridgeshire.
Mr Cameron had said work would start by 2020, but the three biggest Norfolk projects were only granted development consent last year.
The plans for Thickthorn include a new slip road off the A11 northbound, which will take motorists beneath both roads before re-joining traffic on the A47 heading towards Great Yarmouth - eliminating the need to use the Thickthorn roundabout.
The changes would also see a segregated left-hand turn added to those travelling eastbound on the A47, a new footbridge and a fourth lane on the southern part of the junction.
Just over 1.6 miles of the road between Blofield and North Burlingham - considered a crash blackspot by police - are due to be dualled.
Five-and-a-half miles of the road between Easton and North Tuddenham are also due to be dualled.
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