Air quality reports

We are working with the government to help improve air quality in the England by reducing Nitrogen Dioxide (NO₂) levels and supporting the delivery of the UK NO2 Plan.

The government’s Pollution Climate Mapping (PCM) model identifies roads that might exceed the legal limits for air pollution at 40µg/m³.

Some of the roads the PCM has identified are part of our strategic road network (SRN) in England.

We've created a map that shows:

• these locations on our Strategic Road Network
• our latest understanding of the ambient concentrations near these links compared to the annual mean NO₂ limit value

The map also shows:

• the locations of automatic air quality monitors on our road network
• the annual mean NO₂ concentrations recorded by these monitors

The government has asked us to:

• look closely at the areas where air pollution might be too high
• put in measures to reduce pollution as quickly as possible in places where it does go over the legal limits

Air Quality – Annual Evaluation Reports

In response, we published a series of detailed assessment reports, which describe the work we have to do and report on the air quality alongside our network.

For areas where pollution is above the legal limit, we review air quality every year. This helps us see if the NO₂ levels have reduced and if the steps we’ve taken are making a difference.

Air Quality Progress Update Report (July 2021)

Our assessment for each commission is summarised in this Air Quality Update Progress Report.

The report explains:

• the outcome of the phased assessment approach
• which links we assessed as meeting the NO2 limit value
• the actions to achieve compliance on those sites exceeding the NO2 limit value.

National Highways Air Quality Monitoring Network (NHAQMN) reports

These reports give summary results from our air quality monitoring network since its creation in 2016.

We operate a network of automatic monitoring stations across the Strategic Road Network.

Data from these monitors helps us understand Nitrogen Dioxide and, more recently, particulate matter around our network.

Particulate matter (PM) means microscopic solid or liquid particles suspended in the air. These particles are categorised by size - for example, PM_2.5 means particles with a diameter of less than 2.5 micrometres (µm). PM caused by road traffic includes exhaust emissions as well as tyre and brake wear.

This data informs our programme of activity to improve air quality.

If you need help interpreting this information, or more detailed data from a specific monitor, please contact us at Airquality@highwaysengland.co.uk.

Supporting technical information

Here are the technical reports covering our assessment of the PCM links on our network.

As we progress through each phase we update baseline maps and audit reports to include our findings from earlier phases.

If you need help interpreting  this information, or to track down a particular document, please contact us at Airquality@highwaysengland.co.uk.

Commission 1

Commission 2

Commission 3

PCM Link Evaluation Strategy

Following the agreement with the Joint Air Quality Unit (JAQU), a number of links have been identified as above the permissible levels.

We have developed an evaluation strategy to:

• understand and report when each link is compliant
• determine whether any mitigation is delivering the improvements
• confirm when any mitigation can be removed whilst ensuring the section of the SRN remains compliant

Evaluation approach

Air quality monitoring to be deployed for all links confirmed as non-compliant and assessed within 10% of the limit value, i.e. (36-40µg/m³).

Monitoring to be deployed to at least one site as a minimum, but ideally three, alongside the SRN representative of qualifying feature(s).

Monitoring will continue for at least two years after the respective section of the SRN is modelled to come into compliance.

Monitored concentrations will be evaluated at 6 month intervals, (allowing 2 months for tube analysis by the labs):

• mid-year review - end Aug year – covering first 6 months
• annual review and report - end Feb year – calendar year annual average

Removing mitigation will be recommended when concentrations are reported below 36µg/m³.

Air quality speed limit trials - results of research

We’ve trialled 60 mph speed limits on short sections of our network where action needed to be taken to reduce emissions and improve air quality.

Here are the results of our research: