A3 Guildford air quality

Latest updates

• 21 July 2026

  A3 footway closure

  We've completed upgrades along the new route and closed the A3 footway southbound between St John's Road and the A31 Farnham Road junction, where air quality levels exceed the legal threshold.

  Air quality along the A3 has improved significantly in recent years. Monitoring shows that only a small section of footway now remains above the legal annual mean nitrogen dioxide (NO₂) limit of 40μg/m³. This is the only section requiring action. National Highways has a legal duty to investigate and take action where pollution levels on its network exceed legal limits.  

  We've upgraded and signposted alternative routes that avoid areas of poor air quality (see Benefits section below). We'll continue to monitor air quality alongside the A3. Our last published data was included in our Annual Evaluation Report 2025.

  Air quality levels are continuing to improve and, based on current trends, are expected to reach compliance between 2030 and 2035. 
  We'll re-open the footway when there is sufficient evidence of sustained legal compliance and it is safe to do so. 

• 13 April 2026

  Upgrading alternative routes

  We've worked with closely with Surrey County Council and Guildford Borough Council to finalise detailed design plans and agree permanent upgrades to alternative routes away from areas of poor air quality on the A3 footway. 

  From late April, we'll begin enhancement works to improve the safety, accessibility and surfacing of these alternative routes. High level maps of our plans can be viewed within the Overview section of our webpage. 

  We plan to close affected sections of the A3 footway where air quality is above the legal threshold on 27 July, linked to the upgrades to alternative routes. Once there is sufficient evidence that air quality levels will remain compliant, we plan to reopen the footway. 

  We'll continue to closely monitor air quality alongside the A3. As published in our Annual Evaluation Report 2024, we currently forecast that air quality levels will reach compliance in 2030.

• 27 August 2025

  Detailed design

  Since the public information event, we've been working closely with Surrey County Council and Guildford Borough Council to turn our initial concept into detailed design proposals.

  These proposals aim to direct people away from areas of poor air quality to upgraded alternative routes. These upgrades will be reviewed independently through a road safety audit.  

  We'll publish a draft Traffic Regulation Order (TRO) proposal to close sections of affected footway. Subject to the TRO consultation, the closure will come into effect at a later date based on upgrades to alternative routes.   

  From 29 August 2025, a copy of the draft Order, plans illustrating the proposals, alternative routes, and a statement explaining why we propose to make the Order may be inspected at:   

  National Highways
  Guildford Office reception
  Walnut Tree Close
  Guildford
  Surrey
  GU1 4LZ

  During office hours weekdays, until the end of the objection period 19 September 2025.

  Alternatively, these documents may be obtained by contacting us at a3airquality@nationalhighways.co.uk.  

  As published in our air quality Annual Evaluation Report 2024, we currently forecast that air quality levels will reach compliance in 2030.

  Once there is sufficient evidence that air quality levels will remain compliant, we plan to reopen the footway.  

• 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 A31 Farnham Road 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 and monitor 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.