Section 52 is concerned with the duties on Northern Ireland government departments to ensure that net carbon emissions remain below a certain figure and requires departments to act in a manner consistent with the achievement of that objective in the exercise of their functions.

The High Court had quashed the decision to proceed with the A5 on the basis that there was an evidential lacuna in that the potential emissions of the A5 project had not been mapped as to how they would fit into the overall Northern Ireland climate action plan.

The Court of Appeal found that the High Court had erred in doing so and that section 52 does not place an obligation on departments to have its emissions individually mapped onto a precise, quantified pathway before a project can be authorised. It is sufficient that a project is consistent with statutory objectives so far as possible. A project-by-project carbon allocation is not required.

Lady Chief Justice Dame Siobhan Keegan stated: “We are satisfied that there is sufficient evidence which validates the decision made to proceed with the A5 Western Transport Corridor and to establish that the DfI had complied with section 52.  Accordingly, we allow the appeal on all grounds for the reasons we have given.”

The decision has been welcomed by infrastructure minister Liz Kimmins who said that she was “absolutely delighted” with the decision.

Logistics UK chief executive Ben Fletcher commented: “The Court of Appeal’s decision is hugely significant for Northern Ireland and removes what is hopefully the final roadblock for the creation of an efficient A5 Western Transport Corridor. After years of uncertainty, the priority must now be getting this vital road upgrade built, improving safety, strengthening connectivity and unlocking economic opportunities for communities and businesses along the route.

“The A5 upgrade will be one of Northern Ireland’s biggest road schemes and is exactly the type of ambitious infrastructure project that will help businesses strengthen supply chains and create the connectivity needed to drive growth across the region.”

The Alternative A5 Alliance who brought the initial judicial review have said that they will “carefully consider” the judgment.