Drivers face three months of delays during the summer as work is carried out on a major road.
The Highways Agency is widening the A27 at Firle, near Lewes, as part of plans to improve road safety.
Engineers are also constructing a right-turn lane to Burgh Lane and Wick Street and an existing lay-by will be moved 100m farther west.
There will also be drainage works and new road markings and signing.
The work on the 0.8km stretch of road will take place overnight between 7.30pm and 5am and during off-peak hours between 9.30am and 4pm.
The A27 westbound lay-by will be closed while the work is being done.
Burgh Lane and Wick Street will be subject to temporary closures with diversion routes in place.
There will also be two-way traffic lights along with a temporary 40mph speed limit.
Ing Fischer, route manager for the Highways Agency, said: "We advise drivers to allow extra time for their journeys during the works."
The work starts on Monday and is expected to last for 12 weeks.
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