Campaigners are calling for a £47 million road to be scrapped and the money used instead to upgrade the rail line from Bristol to Portishead.
Developers want to build a road through common land between Ashton Gate and Hengrove Road, both regeneration areas in Bristol.
But Pip Sheard, of the pressure group Transport for Greater Bristol Alliance, said reopening the Portishead freight-only rail line to passengers should be chosen for the next round of funding, instead of the road.
However, one councillor, speaking on behalf of North Somerset and the West of England Partnership, has been quoted as wanting to encourage car commuting into Bristol.
Transport campaigners have condemned an idea by some “experts” who want the rail line scrapped in favour of bendy buses.
A plan, called the Core Strategy, says it will promote "reopening of the Portishead to Bristol line for passenger services, or its use for bus rapid transit".
Ms Sheard said: "The idea of running buses alongside an existing rail line is bonkers.”
"The transport link should not be decided on cost but on how much benefit it would bring to people by providing a cheap and reliable service that will get them out of their cars.”
If planners had taken action earlier, the cost of upgrading the rail link to take passenger trains would have been about £7 million. Now it will cost £40 million, still far better value than any bus or road-based plan.
North Somerset deputy leader Councillor Elfan ap Rees said officials were assessing “all options”.
Funding has already been allocated for the Portishead rail link by the West of England Partnership, a body which represents the four councils in the former Avon area.
The partnership's website says: "Reopening the rail link to Portishead is a priority for the West of England."
A spokesman said it was committed to the rail link but could not promise funding would be given by the Government.
More info: portisheadrailwaygroup