Motorways face being covered by “pollution tunnels” to shield nearby homes from exhaust fumes in a plan to improve air quality.
Highways England said that it was considering building tents made from pollution-absorbing materials over the busiest roads to prevent residents breathing toxic fumes.
The agency said it was working on trials using a material that had the potential to absorb nitrogen dioxide (NO2), which is produced by diesel engines and causes lung disease.
Pollution tunnels have been installed in the Netherlands, and officials are working with the Dutch authorities on a design for English roads.
Highways England, which operates motorways and main A-roads, has already installed pollution barriers in a trial scheme alongside the M62 near Manchester.
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In an air quality plan published yesterday, the agency said it could adapt the system into full tunnels to provide greater protection to residents if the costs made it viable.
It also said it was committed to ensuring that rapid-charge points for electric cars were installed every 20 miles on the majority of its network to increase the uptake of green vehicles.
The pollution tunnels were criticised by the RAC Foundation, however. It warned that they risked trapping emissions in an enclosed area and making air quality worse for drivers and their passengers.
The Highways England plan comes a week after the Department for Environment, Food and Rural Affairs published its own plan to crack down on roadside pollution, including a ban on the sale of new diesel and petrol vehicles by 2040. The department identified 81 stretches of road where urgent action was needed to prevent illegally high levels of pollution. These include the M60 in Greater Manchester, the M621 in Leeds, the A1 past Newcastle, the A35 in Southampton, the M32 into Bristol and the M4 near Heathrow.
Highways England, which has been given £100 million to tackle pollution between 2015 and 2021, admitted that “emissions from diesel vehicles are a significant contributor to the poor air quality at the roadside”.
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In 2015, engineers built a 4m high wooden pollution barrier along a 100m stretch of the M62 near junction 18 at Simister, later extending it to 6m. This year, it added a second trial barrier made of the new material, a mineral polymer, which can absorb NO2.
The agency’s new document — a strategy for improving air quality up to 2021 — said it was investigating the possibility of turning this into a full tunnel to trap emissions. “The results from the monitoring of such trials will help us understand if this has been a success with the potential to implement barriers on our network,” it said. “We are also investigating if we can reduce the costs to construct a canopy, which is a tunnel-like structure designed to prevent vehicle emissions reaching our neighbours.” It admitted that the air quality benefits were “still to be fully understood”.
A spokesman said: “The best solution to accommodating the extra traffic on our roads, without negatively impacting on air quality, is cleaner low-emission vehicles. In the meantime we are investing £100 million to test new ideas including less-polluting fuels and road barriers which can absorb harmful emissions.”
Steve Gooding, director of the RAC Foundation, said: “Concentrating emissions in an enclosed environment is the worst thing you can do for people’s health. In the time it takes to get this scheme off the ground we would hope the car fleet will have been significantly cleaned up.”
This year, Highways England confirmed that it had cut the speed limit to 60mph on a stretch of the M1 to see whether lower limits would keep vehicles flowing and cut emissions.
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Yesterday’s document also committed the agency to increasing the number of rapid charge points that can replenish an electric car battery in less than half an hour, saying that it would “work with operators to ensure that this becomes a comprehensive national network”.