Drivers are being warned to expect severe congestion and delays of up to two hours after major roadworks have begun on the Forth Road Bridge.
The work will be carried out for at least 16 weekends
The £3.5m resurfacing programme will affect the southbound carriageway each weekend until the end of June.
It will then be suspended for two months to prevent traffic jams during such annual events as the Royal Highland Show at Ingliston.
Contractors will work between 1800 BST on Fridays until 0600 BST on Mondays.
During the work, ScotRail is to put extra carriages on trains running to and from Edinburgh and Fife to alleviate the road congestion.
ScotRail's operations manager Andy Thomas said:
"As soon as we received details of the roadworks we began drawing up plans to ensure a viable public transport alternative was available."
"By adding additional carriages to these weekend services we are giving more people the chance to beat the traffic jams.
"However, we are expecting services to be busy and would ask customers to take this into consideration when planning their journey."
ScotRail said that on Saturdays, between 0745 BST and 1825 BST, there will be additional carriages on the Fife Circle service, which includes Glenrothes, Markinch, Kirkcaldy and Cowdenbeath.
On Sundays, Fife Circle trains will be lengthened from the start of services up to 1815 BST.
Trains from Edinburgh to Dundee will also have additional carriages from the start of service up to and including the 1715 Edinburgh to Dundee and 1525 Dundee to Edinburgh.
Meanwhile, Fife Constabulary have issued a warning to motorists, reminding them about the misuse of the hard shoulder.
And they urged drivers to allow extra time for their journey, and to exercise "patience and restraint" if caught in a jam.
The force said that the roadworks will cause long delays for southbound traffic on the M90 and A90 roads.
They warn that bridge traffic will be severely delayed, as will vehicles heading for the Pitreavie slip road and the Rosyth and Inverkeithing areas.
Sergeant Mike Jolly said: "Last year, during roadworks in the area south of the Forth Road Bridge, 32 motorists were detected driving on the hard shoulder within the space of one hour.
"All were subsequently fined and had their licences endorsed."
Mr Jolly said that extra patrol cars will be out during the period of the roadworks.