Protestors gathered beside a busy road to call for a bypass before more homes are built beside it.
A planning application is expected soon for 300 new homes off the A10 at West Winch, near King's Lynn.
The properties are the first part of a far larger development, which will eventually total 4,000 new houses on land south of Lynn.
But people living along the busy route fear a roundabout proposed as part of the scheme, next to the former Winch pub, will increase congestion on the already gridlocked route.
They say the plans should be put on hold until a new bypass - being referred to by planners as a housing access road - is built linking the A10 with the A47, bypassing the Hardwick Roundabout.
Funding has not yet been confirmed for the £80m access road.
Retired IT worker Chris Allen, 69, was one of the protestors who lined the road on Thursday.
She said she did not realise how busy the A10 was until she and her husband Brian, 76, bought a house on Lemuel Burt Way, a new development off the A10, in 2020.
"We came from Northampton to view it during lockdown," she said. "We thought: 'What a lovely, quiet little road.
"We didn't realise the traffic was going to be 24/7. They need to build the bypass before they build any more houses.
"You've got to have the infrastructure in place, it's as simple as that."
Trish Field, also retired and in her 70s, lives on a nearby park home development.
"We need the bypass first but they're talking about building another 300 homes," she said.
"So we're looking at another 600 cars coming out of here.
"A roundabout isn't the answer, we need a crossing."
Michele Foster, 66, is registered blind and lives on the eastern side of the A10 - meaning she has to cross to catch the bus into King's Lynn.
"The bus stop's opposite my house but I can't get across the road, I get verbal abuse from drivers," she said.
"I have to walk up to the Hardwick Roundabout to cross and then back to the bus stop. It takes me 20 minutes."
West Norfolk council says it will request a strategic highway assessment of the impact of new development.
Borough councillor Alexandra Kemp quit her role as a portfolio holder and cabinet member in protest.
Ms Kemp, who is also county councillor for South and West Lynn, said: "It's all about making this area safe and sustainable for all ages - people on tricycles, people in buggies, people on bicycles.
"It's completely unsustainable to build a roundabout here, which will increase congestion and accidents.
"It goes against the national policy framework, which says developers must make the area safe for pedestrians and cyclists not just on the development itself but in the surrounding areas."
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