Highways England was initially asked to look at 101 sections of the Strategic Road Network (SRN) based on the Government’s national air quality model, which had identified potential exceedances of the annual mean nitrogen dioxide (NO2) limit values on those sections of the SRN.
Following completion of this work by Highways England, a number of links were confirmed as above the annual mean NO2 limit value. Investigations of possible mitigation measures for these links identified four sections of motorway where reducing the speed limit to 60mph could help reduce levels of NO2. Those sections were:
Due to the impact of the COVID-19 pandemic, and associated reduced traffic flows, Highways England has temporarily removed the 60mph air quality speed limit trials that were already in place on the M6 and M1. Highways England will recommence the speed limit trials when traffic flows are above 85% of their pre-COVID lockdown levels.