Recent court decisions on environmental impact assessment have discussed whether road and utility infrastructure must be assessed as part of "the project"; and difficulties with cumulative assessment when limited information is available.

"the project"/ salami-slicing

Screening is the process of determining whether EIA is required. Difficulties have arisen from planning permission being sought for different parts of a development in separate planning applications (an issue known as "salami-slicing"). The concern is that the EIA process might be circumvented.

The courts have indicated that a development should not be considered in isolation if in reality it is an integral part of an inevitably more substantial development – ie. "the project" to be assessed is the more substantial development, even if consent is being sought for part only.

The "bridge to nowhere" is a rather extreme example. Its purpose is to unlock sites to the east of a railway line for future housing development. After construction, the temporary haul roads were removed and there are no connecting roads on either side. It is therefore of no use at all at present.

Both the planning authority and the High Court considered that the bridge should be assessed as a standalone project. The Court of Appeal disagreed, which shows the scope for different conclusions to be reached on this issue.

The Court also noted the dangers of over-relying on other cases:

"other cases, decided on different facts, are only relevant to the limited extent that they indicate the type of factors which might assist in determining whether or not the proposed development is an integral part of a wider project."

Other recent decisions illustrating the approach taken by the courts include the Llandaff case, where a waste-water pumping station was not an integral part of a large housing development, because it would serve other existing and potential developments; and the Sizewell C case, where there was no requirement to include assessment of a permanent drinking water supply.

Cumulative effects

Environmental impact assessment includes consideration of cumulative impacts from other developments. That means that the cumulative impact of incremental developments will be considered, even if those developments are not assessed together as "the project".

In the Substation Action case, the court upheld the decision by the Secretary of State to grant consent for two offshore wind farms. A future substation extension was at too early a stage to have sufficient reliable information. The court held the Secretary of State was entitled to decide that uncertainties about a future substation extension prevented reliable assessment of cumulative effects, but consent could still be granted.

It can be difficult to decide which cumulative effects to assess. Dr Boswell challenged the decision by the Secretary of State for Transport to grant consent for three road schemes, on the grounds the Secretary of State did not compare the combined carbon emissions from the three schemes along with other local schemes against the UK's national carbon budgets.

The court held it was logically coherent to assess each scheme individually due to the nature of carbon dioxide and the fact it was a assessment against the national budget – scientific guidance advised against combining them.


The "bridge to nowhere" is rare example of court agreeing there has been “salami-slicing”. The court decisions show that two sets of works with cumulative effects are not necessarily a single project, but those cumulative effects can still be assessed, either if EIA is required, or by the planning authority using its general power to require additional information. 

The decisions also show the courts take a pragmatic approach to difficulties assessing cumulative effects, eg. limited information about future projects.