A road through the centre of Lynn will be closed from next week for gas main works, which engineers say will maintain supplies for the rest of this century, to take place.
Drivers will not be able to use the Saturday Market Place for three weeks from next Monday, March 10, while the project to replace pipes in the area is completed.
However, West Norfolk Council says it expects the car park in the square to be open as normal.
National Grid officials say the work, which is expected to take five weeks in total to complete, will replace the existing iron gas mains with modern plastic piping, which is designed to last for at least the next 80 years.
Vince Doggett, authorising engineer for the National Grid, said: “This work is essential to ensure that we can continue to provide reliable gas supplies for local community well into the future.”
Diversions around the closure will be signposted, though access to local businesses will be maintained throughout the closure period.
Mr Doggett said the closure was needed on safety grounds during the first three weeks of the project.
The road will be reopened for the final two weeks of the work, when temporary traffic lights will be in place.
He added: “Safety is our main priority and we have liaised with the highways authority on the traffic management measures.
“We appreciate that our work can cause disruption and we will make every effort to minimise the inconvenience and complete the project as quickly as we can.”
Anyone who has queries or concerns about how the work might affect them is asked to phone the National Grid on 0800 0965678.