The gantry north of the Forth Road Bridge is to be removed as work continues to prepare for the Queensferry Crossing.
Part of the A90 will be closed overnight on Friday and into Saturday morning to allow for the structure to be taken down.
Diversions will be in operation from the Ferrytoll to Admiralty junctions from 10pm on Friday to 6am on Saturday.
The closure in both directions will also allow planned road upgrade works to progress.
Road markings will be altered for the next phases of traffic management.
Workers will also installl an average speed camera system to monitor speed during a temporary speed limit reduction.
A 40mph speed limit is to be introduced from south of the Forth Road Bridge to Admiralty junction.
Project chiefs say reduced traffic speeds are required to ensure the safety of construction operations.
The cameras will be tested for a short period before going live.
A spokesman for Transport Scotland said: “Anyone intending to travel on the A90 during this time should therefore allow extra time for their journey, particularly if they are going to or from Edinburgh Airport.”
Traffic will be diverted through Rosyth, along Milne Road, Castle Road and the A985 Admiralty Road.
Signs will be in place directing motorists.
The works are part of the major upgrade to the road network as part of the Forth Replacement Crossing project.
The 1.7 mile long cable-stayed bridge, which is costing £1.4 billion, is due to open next year.
The Forth Road Bridge is unaffected by Friday’s works and will fully remain open.