Infrastructure Minister Liz Kimmins has ordered officials to “get on with the job” of building one of Northern Ireland’s biggest road projects after a court ruling blocking the work was overturned.

At the Court of Appeal in Belfast, Lady Chief Justice Dame Siobhan Keegan said a ruling by a judge in 2025 preventing the upgrade of the A5 was “problematic” and could not stand.

Proposals to build a new dual carriageway between Londonderry and Aughnacloy in County Tyrone go back almost 20 years but have been beset by funding and legal issues.

Concerns had also been raised about the environmental impact of building a new road and how much farmland it would affect.

However campaigners have for years called on the road to be upgraded, citing its safety record with 57 people having died on the A5 over the past 18 years.

Campaign group Enough is Enough said it was not “a time for celebration” but there was a “sense of pride” over the court decision.

Kimmins, whose department brought the appeal, said she was “absolutely delighted” with the ruling.

She said it was now her priority to “start construction as soon as possible”.

A lawyer for the Alternative A5 Alliance, an umbrella body of landowners, farmers and supporters who oppose the road upgrade, said his clients would “carefully consider today’s judgement”.

He added that his clients “have always been committed to ensuring the A5 project is the subject of the rigour of the law”.

Last year, a court ruled the Department for Infrastructure’s (DfI) plans for the road did not comply with climate change targets, leading to an appeal from the department.

Reading her judgement in the appeal, the Lady Chief Justice described the legal history of the project as “long and torturous”.

She added that she considered four grounds of appeal, including climate change considerations and human rights.

In her ruling, Dame Siobhan said the previous judgement could not stand on climate change grounds and that the project “is a priority investment and should be proceeded with”.

She added that the A5 project was “larger than any road project ever undertaken in Northern Ireland” and that “inevitably this issue intersects with the Climate Change Act”.

The judge said the previous trial judge had “failed to factor in that DfI and the [Northern Ireland] executive were aware” of wider emission issues.

Dame Siobhan also found there were “deficits” in how the original judge considered the issue of human rights.

She said there was “substantial evidence” from the Department for Infrastructure on the issue of how the road would affect landowners and their human rights.

“Overall we find the argument based on human rights to be unconvincing and the judge went too far and made assumptions which he should not have made,” she added.

Dame Siobhan addressed the issue of road safety, describing it as an “obvious and pressing issue given the number of deaths” on the A5.

The judge also questioned why the Department of Agriculture, Environment and Rural Affairs (Daera) was only been brought into the case to deal with climate issues when the case went to appeal.

She added: “The litigation adopted by relevant departments has been unsatisfactory and caused delay.

“We’re not satisfied full thought was given to this case at the appropriate stages.”

Kimmins described the court’s decision as a “hugely positive outcome” but said: “This is about the families, today is their day.”

“The emotions we saw outside the courtroom really encapsulates just how much this means to so, so many people,” she told BBC Radio Ulster’s Evening Extra programme.

The minister said that while she did not have an idea of a revised figure of how much the project would cost, you “cannot put a price on a life”.

“We have a commitment, not just from the executive but across Ireland with our counterparts in the south in the Irish government, and this is a high priority for so many people, so I have no doubt that we can push ahead regardless of the cost.”

The A5 is a 58-mile (93km) stretch of tarmac that traverses the west of Northern Ireland and provides passage to the south.

Although mostly single carriageway with few overtaking lanes, it is a vital artery of the Northern Ireland road network and has more than 200 side roads connecting to it.

The road has remained largely unchanged since the 1960s, with the exception of some town bypasses, but there has been a huge rise in the number of cars, lorries and agricultural vehicles using it since it was first built.

More than 50 people have died on the road since 2006 and there has been a long campaign to upgrade it.

Official statistics show there has been about a 10% increase in traffic on the road in the last 10 years alone, with increase of about 30% forecast over the next 25 years.

A plan to transform the mostly single lane road into a dual carriageway was first proposed nearly two decades ago, with advocates arguing a new, modernised road was needed to save lives.

Those who back the upgrade project, known as the A5 Western Transport Corridor project, have argued it is necessary to save lives.

Those who oppose it, frequently represented by the Alternative A5 Alliance campaign group, believe its impact on farmland and the broader environment will be negative.

The total cost of the cross-border project is estimated to be in the region of £1.7bn.

The Northern Ireland Executive committed about £1.2bn when the final plan was announced by ministers in late 2024.

Irish government funding of €600m (£509m) for an upgrade of the road was announced in February 2024.

Almost £200m has now been spent on the project, despite work having yet to start on the road.

Speaking to BBC News NI, Finance Minister John O’Dowd said that projections in his draft budget over a three-year period “set aside funding for the completion of the A5”.

“The road network in that region has been failed over many, many decades,” he said.

“It now needs upgraded.”