Large "tunnels" covering stretches of motorway to protect locals from dangerous levels of pollution are being considered by Highways England.

The agency said in its latest air quality strategy that it is exploring the possibility of building physical canopies around main roads to soak up car fumes.

In its report, Highways England says it is "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".