A3 Guildford air quality improvements

We are developing proposals to reduce the impact of poor air quality alongside the A3 as it passes through Guildford.

Start date Autumn 2024

End date Autumn 2026

Cost TBC

Latest updates

17 February 2025

Project developments and Public Information Events

We have continued to closely monitor roadside nitrogen dioxide (NO₂) concentrations along the A3 as it passes through Guildford between its junction with Manor Road near the A31 and the Dennis Roundabout / Wooden Bridge junction.

Our monitoring shows areas of poor air quality have reduced, and currently only sections of footway next to the east side of the A3 carriageway (approximately A31 junction to Egerton Road) remain above the legal threshold.

Following a detailed review of options we are proposing to close these sections of footway until air quality improves and re-direct people to alternative routes. The crossing points across the A3 carriageway will be unaffected.

Before closing these sections of footway, we plan to upgrade alternative routes to improve accessibility and surfacing. We are working with Surrey County Council and Guildford Borough Council to develop our designs for these improvements.

We are hosting public information events on Tuesday 4 and Thursday 6 March for people to find out more about the proposed changes:

All Saints Church, Vicarage Gate, Guildford, GU2 7QJ
Tuesday 4 March, 2pm - 7:30 pm
Thursday 6 March 2pm- 7:30pm

More information, including maps of the proposed alternative routes will be added to this page soon.

Following this public engagement, we will continue to develop our proposals in detailed design. We will then seek a Traffic Regulation Order to close the footway.
31 May 2024

Survey and monitoring work continues

We’ve been assessing potential options to address air quality issues on this stretch of the A3 at Guildford to ensure our solution provides the greatest benefits.

We’re continuing to survey andmonitor the diffusion tubes along the route to measure levels of nitrogen dioxide. Diffusion tubes are scientific devices that enable us to passively sample and measure the concentration of nitrogen dioxide.
17 August 2023

Air filtration cube trial update

We’ve been working with a research partner on the proposed trial of air filtration cubes in Guildford. We’re really disappointed to announce that we now won’t be able to run the trial this autumn due to commercial changes within this partner organisation.

We’re continuing with other work to better understand air quality issues along the A3 from the junction with Manor Road to the Dennis Roundabout/Wooden Bridge junction.

See more updates

Project information

We are working with Surrey County Council and Guildford Borough Council to find ways to reduce the impact of poor air quality alongside the A3 in Guildford. This is part of a wider piece of work National Highways is doing to track roadside nitrogen dioxide concentrations where they are above the annual mean legal limit of 40μg/m3.

Learn more about our approach to air quality.

Following a thorough sifting process of potential options, we are proposing to close a section of footway that runs along the affected section of the A3 to move people away from the area where pollution levels are too high. We will seek a Traffic Regulation Order to close the footway and will direct users to follow suggested alternative routes, which we will carry out upgrade work on before the changes are made.

We have previously needed to consider large scale interventions including barriers. Fortunately, with the extent and severity of poor air quality much reduced, we have been developing smaller, less disruptive plans to mitigate the NO2 exceedances on the footway.

About air quality monitoring at National Highways

Air quality is a highly technical area and National Highways is committed to being transparent in our approach to managing it. Our recent monitoring shows that the areas where air quality exceeds the legal threshold have significantly reduced. Currently on the A3 through Guildford, only the section of footway next to the east side of the A3 carriageway (approximately Egerton Road to the A31 junction) remains above legal levels.

We have yet to finalise analysis of data from 2024, but early indications suggest the issue is limited to the footway, and residents' gardens are not in exceedance. We have collected extensive data as part of our research and would like to thank residents who allowed us to install monitoring equipment in rear gardens.

To find out more about the data that has been collected you can view the results for 2023.

To compare with other air quality data visit National Highways Air Quality Mapping (select the NAQMN Report and then select the following layers, NO2 Concentration (ug/m3) and Annual Evaluation Report Diffusion Tube Data and Nitrogen Dioxide (NO2) layers).

For further information please refer to The National Highways Annual Evaluation Report (AER) 2023. 