A5 Court of Appeal revives £1.7bn road scheme

The A5 Court of Appeal has revived Northern Ireland’s £1.7 billion Western Transport Corridor after overturning the High Court decision that had blocked the first phase of the scheme.

In a judgment delivered on 6th October 2026, the Court of Appeal allowed the Department for Infrastructure’s appeal on all four issues before it. Those issues covered environmental impact assessment, human rights, compliance with section 52 of the Climate Change Act (Northern Ireland) 2022 and the High Court’s handling of later climate evidence.

The decision matters well beyond one road. The court has set out a practical test for major projects with carbon consequences: a department must make adequate inquiries and reach a rational conclusion that its decision is, so far as possible, consistent with statutory emissions targets, but it does not have to place every project’s emissions on a precise quantified pathway before approval.

Why the A5 Court of Appeal decision matters

The A5 Western Transport Corridor is a long-running proposal to upgrade the route between Derry and Aughnacloy. The Northern Ireland Executive and Government of Ireland support the scheme on road safety and regional connectivity grounds. The court’s official summary describes it as the largest building project ever undertaken in Northern Ireland.

The first phase had been stopped after the High Court quashed the Department for Infrastructure’s decision to proceed. That earlier ruling found problems with the environmental assessment, human rights analysis and the way climate duties had been addressed.

The Court of Appeal has now reversed that result. The panel comprised Keegan LCJ, Treacy LJ and Humphreys J, with the Lady Chief Justice delivering the judgment.

The ruling is particularly important because Northern Ireland’s Climate Change Act 2022 creates a statutory framework that public authorities must work within when making decisions that increase emissions. The case therefore tested how far a major infrastructure approval has to demonstrate consistency with economy-wide carbon targets before it can lawfully proceed.

Environmental assessment did not need to start again

One ground concerned greenhouse gas emissions from induced cross-border journeys. The challengers had argued that revised emissions estimates required further public consultation and that the environmental statement was inadequate.

The Court of Appeal disagreed. It found that the original traffic model and future-demand modelling had been prepared in accordance with recognised technical guidance and had been accepted by the Planning Appeals Commission as adequate for the environmental impact assessment and public inquiry.

The court also found that greenhouse gas effects had been assessed before the decision was made. The Commission had recommended publication of further emissions statistics, including construction, operational energy and induced-trip emissions. The Department published further material, and the Court of Appeal held that the High Court had gone too far by effectively requiring a new environmental statement.

That is a useful point for practitioners. Environmental information can evolve during a major project’s assessment. The legal question is not whether every later figure appeared in the original environmental statement, but whether the environmental effects were adequately assessed and the decision-maker had sufficient information before making the decision.

Human rights challenge also failed

The A5 project has caused prolonged uncertainty for landowners and residents. The Planning Appeals Commission had recorded severe psychological impacts from years of blight. Its report noted that the scheme would affect 314 farms, involve demolition of eight homes and one traveller site, and temporarily affect direct access to more than 180 dwellings.

The Commission recommended a time limit under which authorisation would lapse if physical construction had not begun by the end of the 2028/29 financial year. The Department rejected that recommendation.

The High Court had treated the absence of a proportionality analysis before that rejection as a procedural failure. The Court of Appeal disagreed. It found that the Departmental Statement gave reasons for rejecting a rigid time limit and that the human rights implications had been considered through the scheme preparation and consultation process.

The appeal court said the potential interference with article 8 rights had been recognised and that the High Court had moved beyond the proper supervisory role when second-guessing the Department’s judgment.

Climate Change Act duty is mandatory, but not an absolute veto

The most important planning-law point concerns section 52(1) of the Climate Change Act (Northern Ireland) 2022. It requires Northern Ireland departments to exercise their functions, so far as possible, in a manner consistent with statutory emissions targets and carbon budgets.

The Court of Appeal confirmed that this is a mandatory duty. Departments cannot simply ignore the carbon consequences of their decisions.

But the court rejected the idea that the duty amounts to an automatic prohibition on a new road or other emissions-generating project. It held that approval is possible where the department has made adequate inquiries and rationally concluded that the decision is, so far as possible, consistent with achieving the statutory targets.

Crucially, the court said the Act does not require the precise greenhouse gas contribution of every project to be placed on a quantified pathway before authorisation. Nor does a project have to be individually identified in a Climate Action Plan before it can be approved.

The official summary records the court’s warning that requiring every individual project to fit specifically within a climate action plan would “stymie all major development in Northern Ireland”.

The legal burden is therefore substantial, but it is not project-specific carbon accounting to the last tonne before a decision can be made. The department must understand the likely emissions, investigate the available policy pathways and consider whether the project would prevent achievement of the statutory targets.

Joined-up government was central to the court’s reasoning

The Court of Appeal also emphasised that the statutory climate obligation operates across Northern Ireland as a whole. The Department for Infrastructure is responsible for transport and infrastructure functions, but it does not control every sector affected by the wider emissions pathway.

The court accepted evidence explaining how project emissions were captured within transport-sector modelling and how those pathways fit into the broader Northern Ireland position. It considered that sufficient to close the evidential gap identified by the High Court.

That does not remove the need for robust evidence. The court expressly criticised the way evidence had emerged during the litigation and described the departmental handling of the case as unsatisfactory. Its conclusion was narrower: once the complete evidential position was before the court, the decision could not properly be characterised as irrational or as a failure of inquiry.

For major development, that distinction is worth keeping in mind. Poor presentation of the evidence can create litigation risk even where the underlying technical work is capable of supporting the decision.

What happens to the A5 now?

The Department for Infrastructure has welcomed the decision and said the ruling provides legal clarity for the scheme. Infrastructure Minister Liz Kimmins described it as “an important milestone” and said the Department would consider the detail of the judgment while moving towards delivery.

The Court of Appeal has set aside the High Court order that quashed the decision to proceed with the first phase. That removes the immediate legal block considered in this litigation, although the scheme still has the practical tasks of procurement, construction programming, land matters and delivery ahead of it.

The wider A5 project has been in development for many years and has already been shaped by inquiry recommendations, environmental assessment and repeated court proceedings. The judgment therefore does not make every future issue disappear, but it changes the legal position decisively.

A Northern Ireland planning lesson beyond roads

This is not an English NPPF case and it should not be treated as one. The statutory framework is Northern Irish, and section 52 of the Climate Change Act (Northern Ireland) 2022 is central to the ruling.

Even so, the case has wider practitioner interest because it addresses a recurring public-law problem: how a decision-maker should deal with climate targets when approving a project that itself increases emissions.

The court’s answer is neither “climate targets are irrelevant” nor “any project with additional emissions is unlawful”. The lawful route is evidence, adequate inquiry, a rational assessment of compatibility with the statutory framework and a decision that remains within the proper range open to the public authority.

That makes the case particularly relevant to infrastructure, energy and other large developments where environmental assessment and statutory climate duties intersect.

Planning Geek has recently covered separate Northern Ireland reforms on major development thresholds for energy projects and the proposed telecoms permitted development changes. Together they underline how quickly the planning and infrastructure framework is moving across the jurisdiction.

Judgment source and case-law position

The Judiciary NI summary identifies the earlier High Court judgments as [2025] NIKB 42 and [2026] NIKB 10. It also states expressly that the full Court of Appeal judgment will be published shortly.

Because the full judgment was not yet available when this report was prepared, Planning Geek has not created a Case Law Library entry from the summary alone. A proper case-law entry should follow the complete judgment rather than a press summary.

The Department for Infrastructure has also published its official response to the decision. Planning Geek is hosting the official Court of Appeal judgment summary locally so the document relied on for this report remains available alongside the coverage.