In some places, the level of emissions was roughly double that amount, meaning that drastic action is required.
To that end, Highways England has identified 30 areas that could use the effort to reduce pollution, and at least nine of those areas will see the speed limit reduced from 70mph to 60mph for the ‘foreseeable future’.
The move comes after a trial that lasted for a year, during which Highways England investigated the impact of slower traffic on the air quality by the side of roads.
Among the areas that will see slower speed restrictions are sections of the M32 near to Bristol, the M1 between Sheffield and Rotherham, and the M5 to Oldbury.
They’ll also implement the rules on parts of the M6 between junctions six and seven, near to Birmingham, and the M602 near to Eccles in Salford.
There’ll also be other areas that will have their speed reduced, after Highways England discovered that loads of roads in the UK have levels of nitrogen dioxide that are too high.
The A34 west of Oxford was found to have unacceptable levels of 69 micrograms per cubic metre back in 2020.
As well as reducing speeds, there will also be diversions in place for HGVs on two sections of the A500 to junction 15 of the M6 during off-peak times.
Highways England’s chief highways engineer Mike Wilson told The Telegraph: “We are committed to supporting the Government to improve air quality alongside and near England’s motorways and major A roads.
“Air quality is within legal limits across the vast majority of our road network, and the picture is improving.”
Drivers could be faced with fines of £100 and up to three penalty points, should they circumvent the rules.
Each year, 40,000 people are thought to die prematurely because of poor air quality, which has led to calls on the government to act.
On top of the speed limits, and HGV diversions, there is also pressure to ensure that lower emission vehicles are starting to proliferate on the roads, with the government outlining plans to ban the sale of diesel-powered HGVs by 2040.