Work to improve the road surface of the A30 near Camborne begins in Cornwall this week.
And in the east of the county essential maintenance work will affect drivers on the A38 in the Glynn Valley.
The Roseworthy dip will be part of the resurfacing scheme which should be complete by the end of the month.
A 2.5 mile stretch of road in both directions will be worked on overnight. Gilberts Coombe Bridge and Blowinghouse Viaduct are also being improved.
During road closures traffic will be diverted via Loggans Moor roundabout.
In east Cornwall maintenance work on the A38 Glynn Valley between Turfdown Cross and the junction with the A390 at Dobwalls will also start on Monday.
The work will include tree and hedge management, gulley emptying, sign cleaning and ecological and geological surveys.
It will also be carried out overnight and involve the closure of the road for eight miles in both directions.
Diversions will be set up.