Motorists have been warned to expect delays on t he Forth Road Bridge early on Saturday morning, and possibly on Sunday, while work to enable an inspection of the main cable is carried out.
Traffic will be cut to a single lane in both directions from midnight to 9.30am on the Saturday.
Further restrictions may be needed from midnight on Saturday until 10.30am on the Sunday, depending on how the work goes.
Queues are expected to build up until the restrictions are lifted but pedestrians and cyclists will still be able to cross the bridge using the west footpath/cycleway.
The inspection involves steelwork being erected near the top of the south tower so that an access platform can be winched into position.
The works are weather dependent and have already been postponed once due to high winds – if they have to be postponed again they will be rescheduled for the next available weekend.
The inspection has been ordered after an increase in wire breaks was discovered in the main cable.
Barry Colford, bridges manager for the Forth Bridges Unit, said: “These restrictions are necessary for safety while steel beams are erected on the main cable high above the carriageway.
“The beams will allow us to hoist an access platform into position so that we can open up the cable for inspection. The purpose is to determine whether the recent increase in wire breaks is indicative of a longer term problem.
“While these breaks do merit further investigation, there are no immediate safety concerns and the cables still have more than enough strength to do their job.
“Once we know the results of the inspection we will recommend any further action that is required to ensure the bridge remains safe and open to traffic.”