Drivers are facing an overnight lane closure on the approach to the Thickthorn Roundabout - because five holes up to 120ft deep are being drilled ahead of a multi-million pound revamp of the junction.
Plans for major changes to the A47/A11 junction, on the outskirts of Norwich, were lodged by Highways England in March.
Proposals include a new slip road off the A11 northbound, before the roundabout, which will take motorists beneath both roads before rejoining traffic on the A47 heading towards Great Yarmouth - eliminating the need to use the roundabout.
A47-Thickthorn-roundabout-proposals (1)
The changes would also see a segregated left-hand turn added to those travelling eastbound on the A47, a new footbridge and a fourth lane on the southern part of the junction.
The Planning Inspectorate will hold an inquiry before making recommendations on whether the changes should be permitted.
Transport secretary Grant Shapps will then decide whether to allow it or not.
But, in the meantime, Highways England has begun ground investigation work in the area around the roundabout.
Five holes are being drilled, which will reach 120ft down, to help the project team understand the existing rock and soil types.
The teams are drilling about 30ft a day and what they find will help them to build the roundabout upgrade swiftly and efficiently, if the revamp work is permitted.
But the work does mean that a lane is being shut on the Norwich-bound A11 approach to the roundabout from 8pm to 5.30am each night, up until Saturday.
Cantley Lane South has also been shut from the A47 to the railway bridge until Friday, July 9, with diversions in place.
Highways England says that noisy work is only being done during the day.
Chris Griffin, Highways England programme lead for the A47, said: "The Thickthorn Interchange connects the A11 to the A47, enabling the growing economic activity around Norwich.
"The current junction can act as a bottleneck who use the roundabout daily, causing queues and slowing journeys.
"Our improvements to enlarge the roundabout and provide dedicated free-flow links will reduce delays at the junction, ensuring smoother and safer journeys.”
If it gets the go-ahead work would start in 2023 and be finished in 2024.
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