Recent News
Natural England’s Standing Advice and Screening Tool for Air Quality Impacts from Roads (STAIR)
The IAQM is delighted to host the STAIR tool for Natural England, its new Screening Tool for Air Quality Impacts from Roads. In due course this will be added to Natural England’s Access to Evidence catalogue.
Please download the zip file to your C drive or preferred location and then enable macros to be able to use the tool. Any queries should not be directed to IAQM, but should instead go to Natural England’s Sustainable Development Team.
Supporting information
As part of ongoing review and development of the evidence base underpinning designated sites and HRA advice, Natural England has considered the use of the commonly applied 1,000 Annual Average Daily Traffic (AADT) screening threshold in relation to air pollution impacts on designated sites.
The 1,000 AADT threshold was originally developed as a proxy screening tool for oxides of nitrogen (NOx) impacts. Recent work has highlighted that the threshold was not specifically designed or validated for wider consideration of nitrogen deposition or ammonia impacts on sensitive habitats. This review reflects a more comprehensive evaluation of the available evidence base rather than any change in environmental standards or legal requirements.
To address this issue, the Screening Tool for Air Quality Impacts from Roads (STAIR) has been developed. STAIR has been designed to provide a more ecologically relevant and scientifically robust screening approach for identifying roads that may require further assessment of potential air pollution effects on designated sites.
The purpose of STAIR is to support proportionate assessment and improve confidence in screening decisions. It is important to note that the identification of additional roads for further assessment does not, in itself, indicate likely significant effects or adverse effects on integrity. Detailed assessment, consideration of mitigation measures, and site-specific ecological judgement will continue to be required where appropriate.
Natural England’s published advice continues to focus on assessing potential effects against established critical levels, critical loads, and the requirements of the Habitats Regulations. The introduction of STAIR is intended to strengthen the evidence base available to competent authorities and practitioners at the screening stage and to support consistent decision-making going forward.
Released: September 2026 (zip, 4 MB)
Download the STAIR Technical Development Report
Released: September 2026 (pdf, 0.4 MB)