Campaigners are set to protest at plans to allow cars and lorries to use part of a bus and cycle route.
West Norfolk council wants to move a bus gate 15m on Harding's Way, in King's Lynn, to open up neighbouring plots of land for development.
But people living around the route fear this will be the first stage of opening up its entire length to all vehicles, while children using it as a safe walking route to school will be at risk from traffic.
Some 1,400 people have signed a petition against opening up the road.
A community rally is being held at the bus gate, near the junction with Wisbech Road, on Saturday (11.30am), to show the strength of local feeling against the plan.
Organiser Kevin Waddington, who lives on nearby Queen's Avenue, said parents at Whitefriars School were opposed to the plan.
Many children from South Lynn use Harding's Way to walk or cycle to school, rather than the congested London Road which runs parallel to it.
"This is the only safe route into town from this area," said Mr Waddington. "You can't use London Road if you've got a buggy or a pram. There are too many sub-roads that cut across it with poor dropped kerbs."
Alexandra Kemp, county councillor for South Lynn, said her authority had ignored more than 100 letters of objection when it granted two traffic orders allowing the change.
"It's a broken promise to the community that they were passed," she said. "They were promised when it became a bus route, it would remain a bus route."
Grandmother Denise Paynter, who lives on Wisbech Road, said if traffic was allowed to use part of Harding's Way parents would be fearful of allowing their children to use the route on their own.
Campaigners fear work on moving the bus gate will begin in October. But West Norfolk council, which is behind the proposed development, said a start date had not yet been set for the work.
It hopes to attract developers who will build homes on land alongside Harding's Way.
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