The Court of Appeal has been told that the planned £1.7bn upgrade of the A5 road was halted due to a misinterpretation of Northern Ireland's climate change legislation.

Tony McGleenan KC, representing the Department of Agriculture, Environment and Rural Affairs, argued that the statutory duty to meet emissions targets does not require a granular analysis of each individual project. Instead, he said, the correct approach is a cumulative assessment of whether overall emissions across the jurisdiction remain on track to hit reduction goals.

The A5 dual carriageway project between Derry and Aughnacloy in County Tyrone was approved by the Department for Infrastructure in 2024. The 58-mile scheme forms part of a cross-border route linking Dublin and the north-west.

More than 50 people have died on the road since 2006, official figures show.

However, in June last year a High Court judge ruled in favour of a group of landowners and blocked the development in its current form. Mr Justice McAlinden found that the department had failed to demonstrate how the project would comply with targets set in the Climate Change Act 2022.

Section 52 of the Act places a legal obligation on Stormont departments to work towards net-zero greenhouse emissions by 2050. Infrastructure Minister Liz Kimmins is now appealing that ruling, supported by Andrew Muir, the DAERA minister.

At the appeal hearing, Mr McGleenan submitted that climate change objectives should not be assessed against individual schemes. He said that officials maintain the upgraded road will not prevent emission reduction targets in the transport sector from being met, nor the overall path to net zero.

The lawyer added that the obligation is discharged by checking the overall emissions profile across nine sectors. The appeal continues.