Repair work is due to start at Hazelwick flyover on Monday (February 11).
Sixteen weeks’ of work will be carried out on the 40-year-old flyover, meaning it will be closed to traffic.
Hazlewick Roundabout beneath the flyover will be reduced to two lanes to give the work crews enough room to work safely during the closure.
Acknowledging that there would be traffic disruption while the work was carried out, a spokesman for West Sussex County Council said: “Motorists are advised to avoid the Hazlewick roundabout where possible while the work is being done.”
The repairs to the flyover have to be made because parts of the bridge have worn over time and are well past their expected service life of 25 years.