Work to reconstruct road and drainage systems will start in the autumn
Drivers have been warned of further delays on the A338 Bournemouth Spur Road as roadworks enter their final stage.
The project started last month and is being carried out ahead of a £26m six-month refurbishment of the route.
Work on the first phase will end on Tuesday night and cones will be moved to the north end of the southbound lane from the Ashley Heath interchange.
The single-lane restriction is likely to cause delays on all approaches.
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.
Dorset County 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.