Mair Bain v Secretary of State for Transport

Paragraph 4.5 of the National Policy Statement for National Networks does not require an up-to-date business case or benefit-cost ratio in every development consent decision. Read with paragraph 4.7, it requires the decision-maker to judge whether the economic information remains proportionate and sufficient to inform assessment of the project’s benefits and adverse impacts, including in light of updated guidance.

Under regulation 21 of the Infrastructure Planning (Environmental Impact Assessment) Regulations 2017, the decision-maker must reach an up-to-date reasoned conclusion on likely significant environmental effects. A formal finding that every item of environmental information is up to date is unnecessary where the conclusion itself addresses those effects. The Tameside duty requires only reasonable inquiry, not the inquiry a court would prefer.

The claimant sought judicial review under section 118(1) of the Planning Act 2008 of the Secretary of State’s decision to make the A38 Derby Junctions Development Consent Order 2023. The Order authorised replacement roundabouts at three A38 junctions.

Permission was granted on ground 1, concerning reliance on a 2019 economic assessment and benefit-cost ratio despite subsequent updates to WebTAG and Treasury Green Book methodology. The claimant alleged misinterpretation of paragraph 4.5 of the National Policy Statement for National Networks, breach of regulation 21 of the 2017 Regulations, and breach of the Tameside duty of reasonable inquiry. A renewed application on ground 3(b), concerning an issue considered in Boswell, was also determined.

The court also considered whether to admit late expert evidence concerning transport appraisal and the benefit-cost ratio.

1. Outcome. The claim was dismissed. The renewed application for permission on ground 3(b) was dismissed as unarguable in light of the Court of Appeal’s judgment in Boswell. The claimant’s application to admit Professor Goodwin’s expert report was refused.
2. Paragraph 4.5 of the NPSNN. Paragraph 4.5 identifies the economic case as a source of information ordinarily provided with a road or rail development consent application. Its purpose is to inform consideration of the project’s economic, environmental and social impacts, and therefore its benefits and adverse impacts under section 104 of the 2008 Act. The information must be proportionate to the development. Whether it remains proportionate is a matter for the Examining Authority and Secretary of State.
3. Updated guidance. Paragraph 4.7 supplies the relevant policy guidance where WebTAG or related methodology changes after the assessment. Updated guidance is expected to be used only where material to the investment decision and proportionate to the investment and its impacts. The Secretary of State therefore asked the correct question in DL22: whether the existing information remained proportionate for his planning assessment. He was not required to obtain a revised assessment or BCR.
4. Environmental impact assessment. Regulation 21 concerns the reliability of the Secretary of State’s own reasoned conclusion on likely significant environmental effects. The detailed climate-change assessment in DL97–DL148 was current and did not rely on the BCR. It therefore satisfied regulation 21(1)(b) and the up-to-date requirement in regulation 21(2). The assessment of alternatives also complied with the statutory and policy requirements, and no direct challenge was made to DL23.
5. Tameside duty. The Secretary of State gave a rational explanation for deciding that the existing economic, environmental and social information was sufficient and proportionate. The duty required reasonable steps to inform himself; the intensity and manner of inquiry were for him, subject to public-law review.
6. Expert evidence. Under CPR 35.1, expert evidence is admissible only where reasonably required to resolve the proceedings. Professor Goodwin’s report was sought principally to answer a defence that was withdrawn. It was not reasonably required for the issues remaining under ground 1 and was excluded.

The judgment is a first-instance decision of the Administrative Court. The court also dismissed a renewed application for permission on ground 3(b), following the Court of Appeal’s decision in Boswell.