Swire v Canterbury City Council: EIA screening, park and ride capacity, and the limits of cumulative assessment

In a judgement handed down on 6 March 2026, Her Honour Judge Karen Walden-Smith dismissed a judicial review challenge to Canterbury City Council's decision to grant planning permission for a new eastbound A2 off-slip road at Wincheap, Canterbury. The decision provides useful clarification on the scope of EIA screening obligations, the Tameside duty of inquiry, and the extent to which a planning authority must assess speculative future development when reaching a screening opinion.

The slip road had been identified in Canterbury's adopted Local Plan as key transport infrastructure to support the regeneration of the Wincheap industrial estate and to reduce congestion on the city's inner ring road. Its delivery was a condition of an earlier outline planning permission for 750 residential units at Thanington Park, with occupation of no more than 449 dwellings permitted until the road was completed. An earlier 2018 permission for the same infrastructure had never been implemented after National Highways rejected the design on safety grounds.

The current application, registered in November 2023, was approved by Canterbury's Planning Committee on 7 January 2025. The claimant, a local resident, contended that the Council had unlawfully failed to assess the environmental effects of the development — in particular the inevitable reduction in park and ride (P&R) capacity at Wincheap, and the consequential need for P&R expansion — under the Town and Country Planning (Environmental Impact Assessment) Regulations 2017.

The EIA screening challenge

The central issue on ground 2 (the sole surviving ground) was whether Canterbury CC had acted irrationally in concluding that no EIA was required. The slip road is a Schedule 2 development, and the claimant argued that the loss of P&R spaces — accepted as inevitable — was a likely significant environmental effect that ought to have triggered a full assessment.

The judge rejected that argument. The slip road was approximately 950 metres in length, well below the 2km indicative threshold in the NPPG. Neither Kent County Council as local highway authority nor National Highways had identified likely significant environmental effects. The screening opinion had expressly recognised the potential P&R capacity impact and concluded that, if timing or extent of works did affect capacity, the developer would be required to demonstrate the absence of adverse effects at application stage. That requirement was subsequently fulfilled through the transport assessment prepared by Stantec, which assumed P&R expansion and was not challenged by Kent CC.

The judge applied orthodox Wednesbury principles. Whether an EIA is required involves an exercise of evaluative judgement, and the court's role is one of review rather than substitution. Canterbury CC's conclusion that the development was not likely to have significant effects was held to be entirely rational.

Cumulative assessment and the limits of foreseeability

The claimant also argued that Canterbury CC was obliged to assess the cumulative environmental effects of potential P&R expansion options — including multi-storey provision or development of the adjacent Wincheap water meadows. The judge disagreed.

Cumulative effects need only be considered where assessment is realistically possible. No worked-up expansion scheme existed. The range of potential variables — expansion onto alternative land, upward development, or a combination — meant that any cumulative assessment would have been based on entirely uncertain foundations. The judge drew on R(Littlewood) v Bassetlaw DC [2008] to confirm that a planning authority is not required to assess developments for which no sufficient information exists. Importantly, the slip road and any future P&R expansion had never been treated as a single project, so no question of unlawful "salami slicing" arose.

Canterbury CC was also not relying on P&R expansion as mitigation. The effects of the slip road development were themselves not considered severe or significant; the financial contribution secured under the section 106 agreement for Thanington Park was a planning benefit, not a required mitigatory measure.

The Tameside duty

No breach of the duty to make reasonable inquiry was established. The Planning Committee had before it the number of spaces to be lost (27 fewer than the previously approved scheme), confirmation of the £1.1 million section 106 contribution, Local Plan policy safeguarding land for P&R expansion, and Kent CC's absence of objection following receipt of further information from the developer. It was rational to proceed without requiring a worked-up expansion proposal.

Section 278

Canterbury CC and the developer sought to rely on the section 278 Highways Act 1980 process as a "backstop" — arguing that Kent CC and National Highways would not enter the necessary agreements unless satisfied there would be no unacceptable adverse impact. The judge found that this argument added little. Section 278 had not featured as a P&R-related safeguard in the officer's report, in the consultation responses, or in the planning committee discussion. Its relevance was confined to highway safety, not P&R capacity management.

The judgement reinforces that EIA screening is a matter of informed planning judgement, not a precautionary exercise requiring exhaustive assessment of all conceivable future scenarios. Authorities are entitled to rely on the absence of objection from statutory consultees, to conclude that speculative mitigation options need not be assessed, and to proceed on the basis that local plan policy and financial contributions provide a sufficient framework for future delivery.

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