Bath's Clean Air Zone has been recognised for improving the city's air quality in the latest government inspection of the scheme, which today (March 15) marks its third anniversary.

It was introduced in 2021 to tackle harmful levels of air pollution caused by the most polluting vehicles driving in the city. The charge does not apply to private cars or motorcycles.

Since introducing the zone the government has recognised its success and more recently acknowledged the council has sustained air quality improvements in Bath for two consecutive years.

Official air quality data from 2022 was submitted to the Government's Joint Air Quality Unit (JAQU) for independent review.

JAQU has now published its full report, officially declaring that the council has passed its 'State 3' assessment. It is the first charging clean air zone to reach this stage.

State 3 is a checkpoint in determining if a clean air zone is achieving success by improving air quality. The State 3 checkpoint is achieved if a local authority has no exceedances of the annual mean Nitrogen Dioxide (NO2) limit value of 40 µg/m3 at valid monitoring locations for a second consecutive year. NO2 is an invisible harmful pollutant which has a damaging effect upon public health. Concentrations are highest at the roadside due to the high contribution road traffic has on NO2 levels.

The report confirms that there was an average reduction of 27% in annual mean NO2 concentration between 2019 and 2022. It also reveals that there were no observations of increased annual mean NO2 concentration across all 125 local diffusion tube test sites, with Upper Bristol Road 4 being the site with the largest decrease in NO2 concentration.

However, the report cautions that the risk of exceedance in future years is high. Factors that contributed to this risk are national traffic data that suggests an increase of traffic in 2023, and fleets less clean than predicted in 2022 due to the impacts the Covid-19 pandemic. The reopening of Bath's Cleveland Bridge at the end of 2022, means traffic flow data for 2023 is likely to be higher. Though, it is noted that the clean air zone is still encouraging drivers to upgrade to cleaner vehicles faster than the natural upgrade rate. The council continues to monitor air quality and traffic flow alongside promoting sustainable travel to help maintain air quality improvements.

Councillor Sarah Warren, deputy Leader and cabinet member for Climate Emergency and Sustainable Travel, said: "It is great to see that all our efforts to improve air quality both inside and outside the zone continue to work.

"We have worked hard to improve air quality within our communities and as we approach our third anniversary of the CAZ, it is pleasing to see that we have sustained these improvements over two consecutive years and been recognised by government for this.

"Everybody has the right to breathe clean air - it is clear, we must continue to lead on building a sustainable future and work to continue to drive down pollution levels further to help protect and improve the health of our residents and visitors."

The State 3 milestone follows the State 2 assessment which the council announced last year.

Later this year, the council will forward data collected from 2023 to JAQU for independent review. 

Bath's CAZ, the first charging zone outside London, was launched on 15 March 2021. Its aim was to urgently tackle harmful levels of air pollution caused by the most polluting vehicles driving in the city.

Older vehicles which do not meet Euro 6 diesel or Euro 4+ petrol emissions standards contribute more towards higher NO2 levels. Drivers of these higher polluting vehicles pay £9 (taxis, minibuses and vans) or £100 (HGVs, coaches and buses) to drive in the zone.

The charge does not apply to private cars or motorcycles. Drivers can check if charges apply to their vehicle and pay a daily charge at gov.uk/clean-air-zones.

The levy is designed to deter higher polluting vehicles from entering the zone, while also speeding up the natural replacement rate of polluting vehicles in exchange for cleaner ones.

Any revenue over the operating cost of the scheme is spent on supporting sustainable transport projects or schemes which contribute towards improvements to air quality.

Find out more about JAQU's assessment criteria.