About 3,500 people have signed a petition calling for the abandonment of plans to turn part of a cycleway into a rapid transport bus route.
Sustrans is opposing the plans
About half the Bristol to Bath path, between Bristol city centre and Emersons Green, is currently the subject of a proposed transit route.
Bristol City Council said no firm decision had yet been made.
Councillor Mark Bradshaw, said: "I share the concerns but this is not a firm proposal."
He added: "It has not come to politicians yet and there is a long way to go."
But Peter Lipman, from the cycling charity Sustrans, said: "The need to improve the public transport system comes out of crowded roads and the way to do that is to take on the roads.
"We should be using road space for buses, we shouldn't be taking away walking and cycling space."
The 16 km rapid Bus Rapid Transit route would run from Emersons Green in South Gloucestershire to Ashton Vale in Bristol.
The cycleway would be widened under the plans.