Work to improve the A43 between Northampton and Kettering is due to start later this month.
Signs have gone up on the A43 near the Moulton end of the stretch of road to inform drivers of the improvement work, which is scheduled to last about 14 months.
It will include a section of dual carriageway being built, reconstruction of the existing Moulton roundabout and a new roundabout at Overstone Grange.
A spokesman for Northamptonshire County Council said: “Improving the A43 between Northampton and Kettering is a key priority for Northamptonshire County Council.
“Without the necessary public funding available, improvements are being made in phases.
“Soon work will start on the A43 Northampton to Kettering stage two, which will see the building of a 1.2km dual carriageway from the existing Moulton roundabout, which will be re-constructed, to a newly built roundabout at Overstone Grange.
“Work is currently due to start at the end of October and is scheduled to last about 14 months.
“To start with, work will take place off the existing A43 and will comprise site-clearance and construction of the new carriageway.
“While these initial works are taking place there will be minimal impact on the travelling public on the existing A43.
“From mid-January, after the busy Christmas period, work will start to affect the existing A43.
“However we are mindful that this is a very busy route so every effort is being made to minimise disruption.
“Traffic management will be used in the form of coned lanes and contraflows but we will endeavour to keep the use of temporary traffic lights to off-peak times.”
The first stage of the work saw improvements to the Round Spinney roundabout to increase capacity at this junction and improve traffic flow.
Signs, which have gone up on the A43 this week, say the work for stage two is due to start on Monday, October 17.