Roadworks on a busy 200-metre stretch of road will see thousands of locals and commuters forced to travel an extra 18 minutes due to diversions.
A small section of Yaxham Road in Dereham will be closed for five days to replace the Mid-Norfolk Railway level crossing, meaning motorists will have to follow a 10-mile diversion route.
The works will see Norfolk County Council close the road in both directions for 24 hours a day, between May 27 and 31.
The roadworks will still give road users access to Greens Road and Walter Road.
Drivers travelling northbound will face three miles of diversions, which would take them up to Etling Green before looping back around on the A47 towards Dereham.
But southbound commuters will have to divert up to Wendling before heading back on Dereham Road through Scarning.
Paul Sandford, landlord and owner of The Railway Taven, which is located next to the closed road, said: "I am a big supporter of the Mid-Norfolk Railway and I know that it is work that needs to be done.
"Our business will suffer but I'm hoping that it will be okay. It is one of them things, we know the works need doing but it's going to be a pain for commuters."
The Yaxham Road crossing is being upgraded after an urgent appeal from the Mid-Norfolk Railway, which raised a total of £150,000 by the public.
In a post on Facebook, the Mid-Norfolk Railway said: "The level crossing is in need for urgent replacement as the electronic equipment is getting old, the track/rails beneath/in the road needs replacing, replacement of the road surface and the lights to be upgraded.
"All to make the crossing easily maintained for the next 40 years and of course improving the safety for all users."
Dereham Town Council noted the application for roadworks in a meeting.
Parishes affected by alternative routes will include Dereham, Fransham, Wendling and Scarning.
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