Forth Road Bridge to re-open tomorrow
Transport experts predicted it would speed up services.
It comes five weeks after the bridge closed when the replacement Queensferry Crossing opened.
New road links have been completed to enable the 54-year-old bridge to begin its new life as a "public transport corridor".
Buses will share one of the bridge's carriageways for the first few weeks.
Non-scheduled buses, taxis and motorcycles will follow in a few weeks' time.
Transport Scotland confirmed the Queensferry Crossing speed limit was expected to be increased from 40 mph to 50 mph "in the coming weeks".
The agency said it was due to become a motorway, with a 70mph limit, "later in the year".
The Forth Road Bridge has been closed to all but cyclists and walkers since the Queensferry Crossing re-opened on 7 September following its official opening by the Queen.
Stagecoach East said services X51, X55 and 747 would switch back to the Forth Road Bridge to restore their previous stops south of the bridge.
Its X5, X9, X54, X56, X58, X59 services will continue to use the Queensferry Crossing.
Mark Arndt, Forth bridges unit account director, for Amey, which will run both bridges for Transport Scotland, said: "We’ve been taking advantage of the Forth Road Bridge being closed to traffic by carrying out important trials and investigations on the carriageway, with a view to completely resurfacing it at a future date.
"We’ve also taken the opportunity to get ahead with steelwork repairs and other maintenance."
Dr Steve Cassidy, Director of transport technology firm ESP Group, said: “Having Scotland’s first public transport-only bridge on an artery road could be very significant for Edinburgh and south Fife.
"The next stage - other buses, taxis and motorcycles - is when we’ll really start to see an impact.
"The public should capitalise on what should be a faster bus service.
"If there is higher demand, operators may also adjust schedules to accommodate additional services."