Worried council leaders are concerned plans to dual part of the A47 do not fully address how the mooted Norwich Northern Distributor Road Western Link would connect to the road.
And councillors have warned that public money could be wasted if the dualling scheme is not designed to link up with that road.
While backing the dualling, they are also worried about the potential impact on other roads, including whether it will heap pressure on the Longwater junction at Costessey.
Highways England has been consulting over its plans to dual five miles of the A47 between North Tuddenham to Easton, as part of a £300m scheme.
Norfolk County Council has lodged its response to that consultation with Highways England, in which it has raised concerns.
One of the prime concerns is how the dualled stretch will co-ordinate with the mooted Western Link, due to meet the A47 at Wood Lane.
Bill Borrett, Conservative councillor for Elmham and Mattishall, said: “I do not see that this junction as proposed will be able to take the predicted future traffic flows once the Western Link is built.
“It is obvious that no sooner than the link is complete, the new junction will have to be redeveloped at great cost, not to mention huge inconvenience to all.”
Tim East, Liberal Democrat councillor for Costessey, said it was “imperative” the Highways England proposals tied in with the Western Link proposals and plans for a food hub at Easton.
Parishes to the south of the A47 are also worried there could be an increase in traffic on routes between Barnham Broom and Wymondham because of the new junction.
Mid Norfolk MP George Freeman has also expressed concern about the impact of drivers using minor roads to get from the A47 to the A11.
The consultation over the dualling closed last month. Work, costing between £100m and £250m, is due to start in 2022, pending consent being granted.
The council has yet to get permission, or funding, for the £153m Western Link.
While it has support from hospital bosses, fire chiefs and businesses, it is opposed by the Wensum Valley Alliance, owners of woodland, the Green Party and the Labour group at County Hall.
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