A second Kincardine bridge has been given the go-ahead by the Scottish Executive after a public inquiry.
The existing bridge is struggling to cope with traffic levels
Transport Minister Nicol Stephen said work on the Forth river crossing should begin next year.
It is hoped the project, which should open in 2008 and cost between £100m and £120m, will reduce congestion on both side of the Firth of Forth.
The bridge will run through the site of the former Kincardine Power Station in Fife and link with the M876.
When the new bridge opens essential repairs will be made to the existing bridge before the two begin operating together.
The twin bridge strategy will divert heavy vehicles from Kincardine itself while avoiding damage to the internationally important bird-feeding grounds at the present bridge, on the estuary's south bank.
The existing Kincardine Bridge, which opened in 1936, is used as a diversionary route during bad weather for vehicles restricted from using the Forth Road Bridge and is now struggling to cope with growing traffic levels.
The new route will start from Bowtrees roundabout at the end of the M876 near Falkirk.
It will cross the river as a wide single carriageway, passing through disused coal yards of the old power station site, through adjoining farmland and join the A977 in a double roundabout junction at Gartarry in Fife.
Work will include a flyover at Bowtrees roundabout, upgrading the A876 between Bowtrees roundabout and the existing Kincardine bridge to dual carriageway and construction of a new roundabout junction at Higgins Neuk at the south end of the existing bridge.
The bridge will be a 1,200 metres long crossing with navigation spans to match the existing Kincardine Bridge.
Mr Stephen said: "This second crossing will improve transport links in Forth Valley and Central Scotland.
'Quality of life'
"It will significantly improve the quality of life for the local community in Kincardine, as well as improving travel for road users in Clackmannan, Falkirk and Fife.
"It will help tackle congestion by improving journeys across the Forth and will provide a valuable boost to the local economy by opening up further development opportunities north of the river."
Scottish National Party transport spokesman Fergus Ewing welcomed plans for a second bridge and said they were long overdue.
"However, the executive's delay in deciding to act could cost the taxpayer about £50m," he added.
"In 2002 this project was costed at £71m, while today it could cost up to £120m.
"We must ensure this bridge delivers best value to taxpayers and the best possible service to users."
But the decision has been condemned by the Scottish Greens, who said completion of the Kincardine-Dunfermline rail link should have been a greater priority.
"This is yet another example of the executive carrying on the Tory road-building project that has resulted in the rising traffic levels and gridlock that we now have in Scotland," the party's transport spokesman Chris Ballance said.