The projects at stake in the judicial review challenge are the upgrading of the Thickthorn roundabout on the outskirts of Norwich, and the conversion of stretches of the A47 trunk road from Blofield to North Burlingham, and from Easton to North Tuddenham, into dual carriageways.
Dr Boswell, a former Norwich councillor, was given permission to pursue the case in December, since when the projects have been on hold.
The focus of Boswell's case is that, in approving the individual proposals, successive transport secretaries failed adequately to consider their overall, cumulative impact on the environment and climate change targets.
The proposals, first announced in 2014, were given ministerial approval through development consent orders last year following a number of public hearings and recommendations from planning inspectors. The Department for Transport is defending the decisions in the case, which is being heard by Mrs Justice Thornton.
Dr Boswell argues, amongst other things, that figures relating to the cumulative impact of the proposals were not included in the final summary shown to transport secretaries, Grant Shapps and Anne-Marie Trevelyan, before the schemes were approved.
Dr Boswell, a former Norfolk Green party councillor, said outside court: “If the cases succeed, all road schemes will have to be assessed for their cumulative impact on climate change”.
A spokesperson for National Highways said: "We stand by our plans and remain confident they can deliver significant improvements to both safety and congestion on the A47, as well as providing a significant boost to the regional economy.”
R on the Application of Boswell v Secretary of State for Transport. Case Number: CO/3506/2022
A version of this article first appeared on our sister title Planning Resource.