England’s clean air zones had raised more than £150m for local authorities by the end of last year, a BBC investigation has found.

Clean air zones (CAZs) are designed to cut pollution by charging drivers a fee to enter certain areas, and have not been without controversy.

Since 2021 CAZs have begun operation in Bath, Birmingham, Bradford, Bristol, Portsmouth, Sheffield, and Tyneside.

An additional £163m was raised in London, which has had a low emission zone since 2008 and an Ultra Low Emission Zone (ULEZ) since 2019.

The idea is to encourage people to take public transport, or drive newer or electric cars that are less polluting.

However, detractors say CAZs are penalising those unable to afford to buy lower-emission vehicles.

So what are councils spending the money raised via clean air zones on – and is it benefiting local people?

The Transport Act 2000 requires local authorities in England to reinvest any excess earnings from clean air zones into local transport plans.

Bristol City Council estimated that by the end of the 2023/24 financial year, it had invested over £6.6m in repairs and improvements to roads and footpaths, encouraging walking and cycling and reducing traffic congestion.

Residents are able access free bike and e-bike trials, adult cycle training, and taster bus and train tickets.

Bradford Metropolitan District Council used £1.7m of proceeds from its scheme to fund a number of transport improvements, including a greener vehicle fleet for the council and an electric vehicle charging network.

The council says it now has the cleanest licenced taxi fleet in the country.

Bath and North East Somerset Council spent £30,000 on a series of bike hangars, which have provided secure storage across the area.

In Bradford, the council has allocated £1.1m to a Clean Air Schools Program, which provides funding to schools to help them implement emission reduction measures on site.

This covers the deployment of wardens to raise awareness of anti-idling outside schools, and projects such as walking buses, bikes, scooters, air filtration systems, and natural green screens that use plants to protect play areas.

Similarly in Bath & North East Somerset, the council has injected £250,000 into a School Streets Pilot scheme to enhance air quality and reduce traffic during school drop off and pick up times.

A number of councils have been putting the money raised so far towards the costs of introducing and operating the CAZ schemes.

In London, the estimated final cost to deliver the expanded ULEZ is expected to be in the range of £145 – 155m.

Newcastle City Council, which runs the Newcastle and Gateshead CAZ, raising £2.4m; and Portsmouth City Council, which raised £1.3m, both said the money has been used to cover running costs.

Local authorities are also reserving money to decommission zones once they are no longer needed – anticipating that drivers will increasingly move to vehicles that won’t be charged.

Deputy leader of Bath & North East Somerset Council, Sarah Warren, said that though there is currently no intention to decommission, should the CAZ cease to operate their reserves would cover costs such as the removal of signage, cameras, cabling, ducting, and power supplies, as well as the disabling of software systems.

A large part of the net revenue generated by clean air zones comes not from the charges, but from the fines that motorists face if they fail to pay the charge.

As of the end of 2023, Bradford Metropolitan District Council had collected more than £3.8m in daily charges, but taken almost double – around £7m – in fines.

Newcastle City Council said that over a year around £1.1m was raised in daily charges to motorists, but fines brought in almost £1.3m.

Bath & North East Somerset Council revealed that between March 2021 and the end of 2023 it raised £8.7m in fines, and £6.4m in charges.

These combined income streams give councils money that they can use for the schemes’ daily operational costs, transport plans, or reserves.

Clean air zones have drawn criticism from those who say they penalise people unable to afford newer vehicles, and have a negative impact on businesses.

Last year London saw an unsuccessful bid to challenge the expansion of the ULEZ, on the grounds that people need more time to swap their vehicles for compliant ones.

Meanwhile in Greater Manchester, the rollout of a CAZ has been on hold since February 2022 after a backlash from business owners who said they would not be able to afford the charges.

Jean Wall, 53, from Bradford runs a mobile sandwich business which she says has been negatively impacted by the city’s CAZ.

In order to get her vehicle from the business’s base to the main road she has to enter the chargeable zone – which means paying £9 every time they need ingredients or fuel.

Ms Wall says the business initially received an exemption for the charges from the council, which was then rescinded after her business partner, who drives the van, moved to Leeds, before it was reinstated and then later rescinded again.

“It’s frustrating,” she said. “It’s just the bureaucracy, it drives you nuts!”

She says that events the business caters to have also reduced due to the effects of the charges.

“It is frustrating that you have councillors who don’t listen to your concerns, and you get a call from this mystery person at the council who says, ‘that’s our decision’,” she said.

A spokesperson for City of Bradford Metropolitan District Council said they were unable to comment on individual cases but that it is the “responsibility of the vehicle keeper to take account of changes in circumstances that may affect the grants or exemptions in place”.

“If the council were to vary the process for distribution of the grants and allocation of exemptions then the government would be within their rights to claw back grant funding which had been incorrectly distributed,” they said.

The council added that its Clean Air Team is happy to discuss any cases with unusual circumstances to explore solutions.