It builds on an earlier trial held in December, which tested the implementation of traffic management without diverting live traffic onto the route.
Traffic will initially be diverted via Kincardine Bridge from 10pm on Friday January 29 while emergency crossovers connecting the Forth Road Bridge to the motorways on either side of the bridge are opened up.
The diversion via Forth Road Bridge is expected to be fully operational by 6am on Saturday morning at the latest.
All traffic will then use the Forth Road Bridge until 10pm on Saturday night, when traffic will again be diverted via Kincardine Bridge while the motorway over the Queensferry Crossing is reopened.
The Queensferry Crossing is expected to reopen by 6am on Sunday morning at the latest, when the Forth Road Bridge will resume its normal role as a public transport corridor.
Chris Tracey, BEAR Scotland’s South East Unit Bridges Manager, said: “The Forth Road Bridge continues to fulfil an important role as a public transport corridor, however it is now also available to provide additional resilience as an emergency diversion route for motorway traffic, should the Queensferry Crossing have to close for an extended period.
“We carried out an initial test of this process in December and are now ready to trial the full diversion, with motorway traffic running on the Forth Road Bridge.
“It should be noted that emergency diversions over the Forth Road Bridge will normally only be implemented overnight, outside peak periods. This is because the process involves laying large numbers of cones and signs, stopping traffic on the M90 and A90, and moving roadside barriers to connect the bridge directly to the motorways north and south of the Forth. This takes several hours and would cause significant additional disruption to traffic during busy periods.
“We will also only divert traffic via the Forth Road Bridge if the Queensferry Crossing is forecast to remain closed for longer than the time it takes to set up the diversion.”