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Natural England’s approach to in combination impacts of car generating plans cannot be supported

In a judgment likely to have far reaching implications for plan-making and development control, Mr Justice Jay has held that Natural England's advice on the correct approach to in-combination effects of car-generating plans "cannot be supported on logical and empirical grounds".

The current guidance identified in the design manual for roads and bridges, has been interpreted by Natural England and many in the planning and environmental world to mean that if a plan or project will by itself generate less than a 1000 annual average daily traffic (AADT) increase on a given sensitive section of road then the impacts of that plan or project can be scoped out.

That was the approach taken by Lewes District Council and South Downs National Park Authority when developing their joint core strategy (JCS). As the JCS would generate well under 1000 AADT on the A26 passing alongside Ashdown Forest European Site, impacts of the JCS on Ashdown Forest were scoped out of further consideration under the Habitats Regulations.

Mr Justice Jay, however, did not accept Natural England's view that the figure of 1000 AADT was sufficiently low to enable plans to be scoped out of consideration either individually or in combination. He concluded Lewes District Council and South Downs National Park Authority should have taken into account the traffic generated by Wealden District Council's core strategy. The traffic generated by both plans together exceeded 1000 AADT so impacts could not be scoped out.

As highlighted above, the 1000 AADT figure is widely use to scope out plans and projects from consideration. It is also used in environmental permitting. The effect of this judgment is likely to be that substantially more plans and projects in the vicinity of European Sites will need to carry out detailed and time consuming studies potentially over a number of years to assess the likely impact of their plan or project on the European Site. Given a plan or project can generate an increase in traffic even some distance away this conclusion has the potential to affect a range of plans projects and permitting decisions.

Certain policies of the JCS have therefore been quashed in so far as they impact on the South Downs National Park. However in a twist the judge accepted that he could not quash the JCS so far as it related to Lewes District Council. That was because a challenge had to be brought within six weeks of the adoption of the JCS by Lewes District Council (the earlier of the two authorities to adopt) and it was no so brought.

Implications of this decision:

  • When scoping a plan or project for impacts on a European Site it will be necessary to decide if the plan or project will increase traffic through the European Site by more than 1000 AADT in combination with other plans or projects in the area.
  • When bringing a challenge to a joint development plan it is necessary to bring the challenge within six weeks of adoption of the plan by the first authority to adopt, it is not sufficient to bring the challenge within six weeks of the adoption by the second authority to adopt.

Lewes District Council and South Downs National Park Authority were represented by James Findlay QC and Clare Parry. Click here to view the judgment.