Andrew Boswell, R (on the application of) v Secretary of State for Transport

In environmental impact assessment, the identification, description and assessment of cumulative effects are matters of evaluative judgment for the decision-maker. The court applies a supervisory standard: whether the decision falls outside the range of reasonable decisions or contains a demonstrable flaw in reasoning.

Where greenhouse-gas emissions are assessed against national carbon budgets, and their effects are global rather than geographically confined, the decision-maker may reasonably decline to compare the combined emissions of selected local projects against those budgets. The EIA regime requires a proportionate assessment based on current knowledge and methods. It does not require a perfect assessment or impose one prescribed methodology.

Dr Boswell brought judicial review proceedings challenging three development-consent decisions concerning nationally significant A47 road schemes in Norfolk. The Secretary of State had assessed each scheme’s construction and operational carbon emissions against the United Kingdom’s national carbon budgets. The assessments also incorporated other developments in traffic modelling and produced combined emissions figures, but the combined figures were not themselves compared with the national budgets.

The central issue was whether that approach breached the Infrastructure Planning (Environmental Impact Assessment) Regulations 2017, particularly the requirements concerning cumulative effects, and whether a fallback assessment undertaken for two schemes was lawful.

1. The claims were dismissed. The Secretary of State’s approach to cumulative carbon emissions was lawful and did not breach the Infrastructure Planning (Environmental Impact Assessment) Regulations 2017.
2. The question of which impacts should be addressed cumulatively, how they may occur, whether they are likely to be significant, and how they should be assessed involves evaluative judgment. The court’s role is to decide whether the judgment falls outside the range of reasonable decisions or contains a demonstrable flaw in reasoning. The views of the Secretary of State and examining inspectors, as primary judges of fact, attract considerable weight.
3. The environmental statements and decision letters recognised the relevance of cumulative effects. The “Do Something” figures described the combined emissions from the three schemes and other relevant development. That satisfied the requirement for a description of likely significant effects resulting from cumulation. The EIA process continues beyond the environmental statement, through examination, consultation and the decision-maker’s assessment.
4. The use of national carbon budgets as the benchmark for significance was lawful. There was no challenge to that benchmark. Greenhouse-gas emissions have global effects rather than a geographically limited effect, and the scientific basis for treating them differently from other EIA topics warranted substantial judicial respect.
5. In that context, it was rational not to compare the combined emissions from a selected group of local schemes against a national, economy-wide target. There was no single prescribed methodology, and selecting particular local projects for comparison could be scientifically arbitrary. The fact that another approach might be more suitable did not make the adopted approach unlawful.
6. Concerns about the limited value of comparing an individual project with a national target concerned the acceptability of the impacts and the merits of climate policy. Those matters were for the Secretary of State, not the court. It was unnecessary to decide the lawfulness of the fallback assessment for Schemes 2 and 3.

First-instance judicial review proceedings. The judgment does not state any prior appellate decision in the same litigation.