New measures to further improve air quality and protect Bath city centre and the wider World Heritage Site, including Cleveland Bridge, are to be considered by Bath & North East Somerset Council's cabinet.

A report to cabinet on Thursday 16 December says since Bath's Clean Zone was launched last March air quality in the city has improved, but still breaches national limits in a number of areas, including at sites around Cleveland Place.

To tackle this, the report recommends that cabinet explores a variation to the Bath Clean Air Zone Charging Order 2021 so that all Euro VI diesel powered vehicles exceeding 12 tonnes become chargeable under the scheme.

It also recommends that the council considers strengthening its transport policies should there be a need to go further to protect the amenity of the city, continue to improve air quality standards, reduce vehicular demand on road space, and respond to the climate and ecological emergencies already declared by the council.

Under the proposal vehicles weighing under 12 tonnes would remain unaffected. In recognition of the considerable fleet improvements already made by owners and operators of heavier HGVs, and to protect local businesses and their supply chains that have recently invested in Euro VI diesel vehicles, a time-limited exemption is also being proposed to complement existing exemptions for hybrid, electric and alternatively fuelled vehicles.

The report says that while HGV operators should be applauded for moving quickly to improve their fleets, with only a handful of larger, non-compliant HGVs now entering the CAZ each day, there is now an opportunity to move further and faster to encourage increased uptake of hybrid and alternatively fuelled vehicles and remove heavier diesel HGVs from the city. This should further improve air quality and the amenity of the CAZ area and wider Bath World Heritage Site, including the Grade II* listed Cleveland Bridge which is undergoing an extensive £3.8m renovation.

Councillor Manda Rigby, cabinet member for Transport said: "The issue of heavy vehicles using this unique and historic city as a through route has long been a problem for residents.

"And while we have made great strides in improving air quality in the city through the introduction of CAZ, there are still hotspots where pollution exceeds government targets particularly around Cleveland Place.

"To improve air quality and protect the amenity of the city, we had considered restricting HGV movements over the bridge. However, this has the potential to divert traffic onto roads in neighbouring authorities. I therefore welcome this opportunity to consider the recommendations to extend zone charges to the heavier Euro VI HGVs, and also to strengthen our transport policies."

If the proposed variation to the Charging Order is approved, it would be subject to further feasibility work to develop and implement a workable scheme. The council also intends to consult with haulage trade associations, neighbouring authorities, National Highways and the Secretary of State as a next step. Other options explored include:

:Charging HGVs for using roads outside the CAZ

However, the report says these options are unviable. It also suggests the long-term solution would be to make the A350 the strategic route between the M4 and Dorset Coast thereby limiting the use of Cleveland Bridge, while the council continues to work with Wiltshire and Dorset councils and the Sub-Regional Transport Board (STB) Western Gateway to complete a strategic study into this proposal, it is unlikely to yield a solution in the short-term.