The measure will be introduced later this month on the M6 north of Birmingham (junctions six to seven), the M1 close to Rotherham (34 to 33) and on the M602 near Eccles in Greater Manchester. A 60mph limit will be installed at a fourth site on the M5 near West Bromwich (junctions one to two) at a later date.

The four sites were identified as locations where nitrogen dioxide levels exceed the annual legal limit. According to Highways England reduced speeds should bring forward the date when the sites comply with emissions standards by up to two years.

It adds that the reduced speed limits should only have a negligible impact on journey times, given the short stretches of roads involved.

Highways England’s head of environment Ivan Le Fevre said: “Ultimately the air quality challenge will be solved at the tailpipe by vehicle manufacturers and changes in vehicle use. Until this happens we will continue our extensive programme of pioneering research and solutions.”

He added: “The speed limits trial will stay in place until the shift to cleaner vehicles means we can remove the restrictions and maintain cleaner air.”

Initial assessments show that managing speed at 60mph can result in an average 17% reduction in vehicle emissions. Further roll out of reduced speed limits could follow elsewhere on the motorway network in areas found to have air quality issues.

The 60mph speed limits will be clearly displayed on roadside signs and be in operation 24 hours a day. Highways England says that keeping the maximum speed down around the clock is necessary because vehicles travelling late at night often travel at higher average speeds, leading to more emissions.

Introduction of the lower speed limit on four stretches of motorway received a cautious welcome from Asthma UK and the British Lung Foundation’s policy officer Zak Bond.

“While it’s always positive to see measures being introduced to try and improve air quality on sections of our busiest motorways, much more needs to be done to reduce air pollution caused by vehicle use – particularly in towns and cities.

“To make a greater impact on harmful emissions, there needs to be a big reduction in vehicle use and a major shift towards electric vehicles,” Zak added. “Clean Air Zones in the most polluted towns and cities should be implemented without delay to reduce levels of nitrogen dioxide and fine particulate matter, dangerous pollutants that come from vehicles.”

The Road Haulage Association's head of policy for environment and regulation Chris Ashley said: “We are watching this development with interest. Clearly congestion causes emissions, so if traffic flow is improved by reducing the speed limit and this leads to a reduction in emissions it is worth looking at.”

But he added that it would be a concern if the reduced speed limit was found to exacerbate congestion.

(Photograph: Highways England)