Drivers of so-called dirty vehicles in Bristol could be forced to pay a charge to drive into the city centre.
There are plans to create a Clean Air Zone in the city in a bid to cut down on pollution.
Taxi drivers have been warned they may have to pay a daily fee - but the charges would also apply to other motorists.
Which vehicles could be affected?
The most likely cars to be incorporated under the charge includes:
private hire vehicles
diesel cars made before last year
petrol cars made before January 2005
Why is the charge being considered?
The city's air quality is illegally low - and European politicians say tougher laws are needed.
Clean Air Zone charges are needed to address air pollution in Bristol. The different charging criteria for petrol and diesel reflects the fact that diesel vehicles emit much higher levels of pollution than petrol vehicles.
A similar low-emission scheme covers most of London.
It is far too early to consider what Clean Air Zones will mean for Bristol and how we achieve better air quality. I have announced and will soon launch a congestion task group and that will look at improving traffic flow and improving air quality. The congestion task group will have a wider remit but it is our intention to create a Clean Air Zone by positive actions in consultation with our bus operators, taxi drivers and all road users.