The vital crossing was shut at midnight on Friday after a 20mm-wide crack was spotted in a steel truss under the southbound carriageway.
Transport minister Derek Mackay said the shock decision to close was taken “within minutes” of ministers being informed of the fault.
And he insisted that repair work on the structure should be finished in early January, contradicting claims by one expert that it may never open again to heavy vehicles.
But fears have been raised over the country’s ability to cope as yesterday morning trains were rammed with stressed commuters.
Last night the city council announced all major roadworks have been suspended in an effort to minimise disruption, with city bosses also contacting utility companies to request they call a halt to everything except emergency works.
Meanwhile, ScotRail laid on 8000 extra seats – but large queues still formed at Inverkeithing and Dunfermline stations, with crowds also swelling at Waverley for services running in the opposite direction.
At Dalmeny station, the council was forced to bring in extra parking restrictions as vehicles spilled out of the car park and on to surrounding streets.
One commuter told the Evening News he had been forced to miss his 6:17am train from Inverkeithing because the carriages were overflowing.
He said: “It was just absolute carnage, to be honest with you. There must have been 200 people on the platform. Mostly it was a safety hazard, that many people on the one train.”
ScotRail said it was launching an extra 5:52am service from Inverkeithing to Waverley to increase capacity.
On the roads, Forth Bridge operator Amey confirmed a vandal had taken a “brick or rock” to a restriction sign on the A985, forcing bosses to find a replacement.
And the official Twitter account for the bridge said that officials had to “prevent cyclists and pedestrians getting onto the bridge to take ‘selfies’”, adding: “It hampers work and puts people at risk.”
Drivers commuting from Fife to Edinburgh can currently expect their journey time to more than double at peak times as they divert via the Kincardine and Clackmannanshire bridges.
John Chalmers, principal clerk to the Church of Scotland’s General Assembly, lives in Dunfermline. He said his commute to the Capital took an hour longer than usual despite his decision to beat the morning rush by leaving later.
He said: “I don’t think it would have been so bad if it was not so wet. I dread to think what happens if it is not open again after New Year.
“I guess it would have taken me about three hours if I had left at my normal time of 7am.
“I will get better and they will get better, but it’s still going to take 40 to 50 minutes longer than otherwise.”
He said his daughter, a nurse at the Western General, had to start at 7:30am. “She lives in Crombie, right on the A985, which was closed to all but buses and heavy good vehicles. The first day the bridge was closed, she left at 5:30am and didn’t get home till 9pm.”
Mr Mackay said: “We recognise many people are travelling earlier, therefore an early morning train will be added to the timetable by ScotRail, along with 8000 extra seats.”
Transport Scotland said last night the A985 bus/HGV priority route will reopen to all traffic overnight between 8pm and 5am from now until the Forth Road Bridge reopens.