West Sussex County Council has chosen VolkerFitzpatrick to work on the design and build of major improvements to the A259 north of Littlehampton.
The scheme will see sections of the A259 become dual carriageway between the new Fitzalan Link Road and the A280 roundabout.
The changes will ease congestion, shorten journey times and make it easier to reach new housing and workplaces.
The full list of improvements includes:
The project is one of a number of major schemes being developed to improve infrastructure in the Arun area over the next three years. Works are scheduled to start in summer 2018 and last up to 18 months.