Sections of the M1 near Rotherham, the M6 near Witton and the M5 to Oldbury have all been limited to 60 mph in recent months to reduce illegally high levels of nitrogen dioxide emissions.
Highways England will keep the change in place for the ‘foreseeable future’ until pollution drops well below legal limits. Four other zones have speed limits in place for other reasons, such as road works, and will have 60 mph limits imposed when these temporary measures end.
Highways England has identified 30 areas of its road network where NO2 levels exceed legal limits of 40µg / m3.
This includes a section of the A3 near Guildford where the limits are more than double the legal limit. Highways England is now considering the introduction of a 9.3 meter high barrier.
It also plans to divert heavy goods vehicles from two sections of the A500 to junction 15 of the M6 during off-peak hours. A section of the A38 north of Plymouth will also be considered for new lower speed limits once its air pollution levels are assessed.
NO2 pollution from vehicles has been linked to asthma and exacerbates other respiratory conditions.
Highways England said the “long-term” solution to the pollution was the introduction of electric vehicles, which it supports in cities like Nottingham and Bristol, including “try before you buy” electric van centers for local businesses.
But he admitted that in 17 of the 30 areas, he had “no viable measures available” to reduce air pollution in a shorter period of time.
Mike Wilson, Chief Motorway Engineer at Highways England, said: “We are committed to helping the government improve air quality along and near motorways and major A-roads in England. Air quality is within legal limits on the vast majority of our road network, and the image is improving. ”