Work to reduce traffic delays at the Pease Pottage junction of the M23 will take 9 months to complete.
It is scheduled to start on March 18.
The aim of the project is to reduce congestion and time coming off the motorway, and accessing the Moto service station.
Tim Canham of Breheny Civil Engineering said “We are giving plenty of notice about these improvement works to J11 so that drivers can plan ahead.
“Delays may be incurred during the works. The Pease Pottage service station will be accessible throughout the works.
“There will be infrequent road closures but these will be overnight to minimise disruption.”
Brighton Road’s capacity will be doubled to become a dual carriageway to a new four-arm roundabout to the Moto service station and the entrance to the new housing development by Thakeham.
A spokesman said: “Other improvements are for pedestrian and cyclist safety with the upgrading of Horsham Road bridge’s existing uncontrolled pedestrian crossing to a signal-controlled crossing and the installation of a signal-controlled crossing on Brighton Road.
“These improvement works were requested by West Sussex County Council and Highways England, and are part of the substantial investment in infrastructure that Thakeham are delivering with thenew homes.
“The timing was chosen to minimise any delays brought about by inclement weather events.
“The high amount of traffic using J11 is causing delays, so widening works to increase capacity are necessary to make journey times more reliable.”