An A-road in Dorset is set to have its speed limit cut after a long trial showed the move would improve air quality. The A35 will now feature an extended 30 mph limit near the village of Chideock, with Highways England claiming the change will help to reduce nitrogen dioxide pollution in the area.

The organisation, which is in charge of the country’s motorways and major A-roads, says it trialled the reduced 30 mph speed limit to monitor the change in pollution. Although Highways England itself admits the trial revealed only a “small reduction” in pollution levels, the company deemed that sufficient reason to cut the speed limit permanently.

The move is part of an ongoing Highways England initiative to investigate measures that may improve air quality on and alongside the strategic road network. The organisation claims to have developed a “programme of measures” that improve air quality at locations around the country, with traffic management and speed limit management all in play to reduce emissions.

Diesel emissions

Chideock was identified as an “air quality management area” by Dorset Council, the pollution control and monitoring authority, so Highways England trialled a new 30 mph speed limit on the A35 at the western end of the village in September 2019. The 18-month trial involved monitoring equipment, regular patrols and the 30 mph speed restriction.

Andy Roberts, Highways England’s route manager for the A35, said the extended 30 mph zone would be joined by an electric vehicle charging point in the village as the organisation attempts to cut pollution.

“We have a responsibility to tackle pollution caused by vehicles using our network and we’re working in partnership with Dorset Council to improve air quality in Chideock,” he said. “As part of our ongoing work, we undertook and completed a trial which saw additional diffusion tubes installed and an electric-powered van monitoring real-time pollution before and after the speed limit change.

“This identified a small reduction in nitrogen dioxide levels following the reduction of the speed limit and as a result of the localised air quality benefit, we propose to make the extended 30 mph zone a permanent fixture.

“We have also funded and delivered an electric vehicle charging point in the village, and although the air quality challenge will ultimately be solved at the tailpipe by vehicle manufacturers and changes in vehicle use, we will continue to work with Dorset Council and monitor air quality.”