The definition of the grey belt was one of the main points to come out of the December 2024 update to the National Planning Policy Framework (NPPF). The updated guidance defines the grey belt as “land in the green belt comprising previously developed land and/or any other land that in either case does not contribute strongly to any of the green belt’s purposes, but excludes sites protected on another environmental, social or historic basis”. The NPPF states that these sites should be prioritised for development ahead of other areas of the green belt or greenfield sites.
Bethanie Helas
A number of developments previously refused planning permission in the green belt have since gained permission on appeal based on their location within the grey belt. Developers wishing to submit a planning application for a green-belt scheme will stand a much greater chance of success if they opt for ‘grey’ land.
Subsequent updates to the green-belt planning practice confirmed that local plans and strategic land releases should be informed by a green-belt assessment, which should be sufficiently granular to ensure robust results. This has been upheld in some recent appeals, with inspectors criticising the use of overly large assessment parcels. Existing green-belt assessments will therefore need to be reviewed to ensure they meet the latest guidance on identifying grey-belt sites, as part of the process of green-belt land release.
The solution lies in using a geographic information system (GIS) to run a multi-criteria evaluation (MCE): a decision-making tool combining multiple criteria into a single map to help solve complex problems. It is commonly used to conduct site searches, as well as environmental management and disaster risk assessments.
To identify grey-belt sites, a GIS can immediately access diverse datasets on land use, environmental and planning constraints and settlement boundaries, based on the NPPF’s defining criteria. Locally applicable information (such as relevant land zoning from existing local plans) can also be utilised. A GIS also enables sophisticated proximity analysis of roads, railways, water bodies and existing development.
The NPPF has increased the need for green-belt assessment at all stages of the planning process
Physical modelling of topography can be conducted over large areas and incorporated into the MCE. This is especially relevant when identifying grey-belt sites, as national guidance states that areas enclosed by existing development or contained by physical features are less likely to strongly contribute to the green belt’s purposes.
Standardising site analysis
Comparing multiple criteria or datasets can become complex. However, with a GIS, measurements can be standardised to create conformity and ease of comparison. Weighting, scoring and ranking of criteria and analysis of data layers is then used to produce a single map highlighting areas with a high, medium or low likelihood of being grey-belt sites, providing visual, data-driven guidance to both policymakers and developers.
Green to grey: the NPPF’s definition of grey-belt sites is helping to bring forward more green-belt schemes Credit: shutterstock
Additional GIS analysis can also be applied to extract and map grey-belt sites with clearly demarcated boundaries. The number or area of grey-belt sites identified can be set to meet the authority’s needs, if known. If taking the latter approach, extra socioeconomic criteria and travel times to essential facilities can be incorporated into the MCE to prioritise more sustainably located grey-belt sites in the areas of greatest need.
All this analysis can be conducted over large areas at a fine level of granularity, without the need for pre-defined parcels. As well as avoiding potential criticism during appeals, this increases the likelihood of identifying smaller grey-belt sites and reduces the need for multiple assessments. Even with this level of detail, the end results can be achieved within hours, as opposed to weeks or even months using more traditional methods.
The revised NPPF has increased the need for green-belt assessments at all stages of the planning process.
As developers increasingly look to utilise grey-belt sites, and local planning authorities look to identify additional locations for sensitive development to meet their housing and employment land requirements, utilising the GIS will be a major advantage in reducing delays, appeals and administrative burdens.
Bethanie Helas is GIS consultant at Lanpro
