Bristol Clean Air Zone could be scrapped in 'three to four years'

It is hoped the clean air zone will reduce air pollution in the city

A city's clean air zone could be scrapped in "three to four years", if air pollution falls.

Modelling by Bristol City Council shows the city's air quality could improve enough by then to remove the scheme.

It was launched just over a year ago after the government said the council had to reduce air pollution to within legal limits.

If levels of pollutants fall to below those limits, then the clean air zone could be abandoned.

The council's executive director of growth and regeneration, John Smith, said: "The timeframe for the Clean Air Zone is driven by the legal compliance issue, so that determines how long it lasts.

"There's not an immediate switch off if we reach compliance, because there's a further period of testing. But we're assuming another three to four years."

This would mean drivers of older diesel cars and other non-compliant vehicles would be allowed to drive through the centre of Bristol without paying a charge or a fine.

The clean air zone covers the city centre and some approach routes

An update on the scheme was given to the council's resources scrutiny commission on Friday, the Local Democracy Reporting Service said.

Nitrogen dioxide is one of the most harmful pollutants, and is largely caused by road traffic.

Under the current law, annual average concentrations cannot exceed 40 micrograms per cubic metre of air.

But the law could be tightened up and limits reduced further, meaning if "the goalposts are changed" then the Clean Air Zone would have to remain in Bristol for longer.

It is unclear how much pollution has fallen since the clean air zone was launched in November last year, but full details of its affect on air quality, as well as how much drivers have paid the council, should be published next month.

An updated report with these details was expected this month, but the council said analysis of air quality was taking longer than expected, for which Mr Smith apologised.

Deputy mayor Craig Cheney said the council would not provide data on just the financial income in the meantime, adding: "We've been keen to bring, for the sake of public discourse, the two together at the same time."