Work to reconstruct road and drainage systems will start in the autumn
The final stage of works on the A338 Bournemouth Spur Road will take place at night, Dorset council has said.
The verge clearance project started last month and is being carried out ahead of a £26m six-month refurbishment of the main route into the town.
The single-lane restriction has been causing delays on all approaches.
From Wednesday night, the cones will be moved to the north end of the southbound lane adjoining the Ashley Heath roundabout.
The restriction will be lifted each morning.
A county council spokesman said the vegetation on this section of the road was not as dense as other areas where it was necessary to use heavy cutting equipment that can only be used during daylight hours.
"It is sufficiently safe for the workforce to carry out the work overnight," he added.
He said the verge clearance work was due to be completed within two weeks.
A single-lane restriction will also be in place overnight on the northbound carriageway while reptile fencing is erected along a three-mile (5km) section.
The work is being carried out to clear trees and scrub vegetation and reclaim drainage ditches in the verges adjacent to the A338 to solve problems of carriageway flooding.
Ecologists carried out work to relocate a number of protected species of reptiles from the verges in November 2009.
The council said any remaining wildlife would be moved in the spring after preliminary work was completed.
The reconstruction of 6.5 miles (10.5 km) of road and drainage systems is due to start in the autumn.