Clearance works along the A2300 in Burgess Hill are due to start next week, the county council said.
The works are in preparation for a £23million highway improvement scheme that is expected to start in spring 2020.
The clearance of trees and vegetation will start on Monday (September 16), weather permitting, the council said, and is expected to take between six to eight weeks.
Roger Elkins, West Sussex County Council cabinet member for highways and infrastructure, said: “This clearance work is essential preparation ahead of the major A2300 improvement scheme, which will widen around 2.5km of single-lane road to a dual carriageway.
“A significant amount of residential and commercial development is planned for the north and north-west of Burgess Hill and this will exacerbate the current traffic issues on the A2300.
“The improvements scheme will reduce congestion and so cut both journey times and pollution. We will also be providing new facilities for both pedestrians and cyclists to help promote sustainable transport.”
The clearance work will take place between the A23 at Hickstead and the proposed Northern Arc site access roundabout – west of the junction with A273 Jane Murray Way.
None of the trees to be cleared are subject to tree preservation orders and there will be a replanting scheme, said a council spokesman.
They added: “This work is essential to enable pipework and utilities equipment to be moved and protected as the major road scheme progresses.
“It is expected that there will be little impact on traffic.”
The majority of the funding for the scheme will be provided by central government through the Coast to Capital Local Enterprise Partnership, with the rest coming from the county council and developer contributions.
Jonathan Sharrock, chief executive at Coast to Capital, said: “This scheme aims to develop this road into a dual carriageway and therefore, hugely improve the roads capacity.
“This will reduce journey times and congestion, improve links to homes and businesses and encourage new infrastructure that will contribute to the local economic growth.
“We are delighted to see progress with the scheme and look forward to working closely with partners on developments.”
The road widening will take place between the A23 at Hickstead and the proposed Northern Arc site access roundabout.
Pookbourne Lane/Stairbridge Lane junction will be amended to become a left-in/left-out only junction and Bishopstone Lane junction will turn into a left-out only junction.
Minor alterations will also be made to the A23 roundabout at Hickstead and Cuckfield Road roundabout to accommodate the new dual carriageway.
A new off-road shared footpath and cycle path will be provided to the north of the dual carriageway.
More details can be found on the county council’s website by searching for ‘A2300 corridor improvements scheme’.