LABOUR is to give the go-ahead for building a second crossing over the River Forth to ease congestion on the existing road bridge.

The party is expected to include a commitment for a new bridge or tunnel — at a cost of up to £1 billion — in its manifesto for next year’s Scottish election.

The move follows increasing concern about the condition of the existing bridge, built 42 years ago, including corrosion of the two main cables from which the road is suspended.

Experts have warned that the bridge might have to close to heavy goods vehicles by 2013 and to all vehicles soon afterwards. But it could take up to 10 years to build a new bridge.

The bridge was designed in the 1950s for a traffic volume of 11m vehicles a year but currently carries more than 24m a year. It is safe for the bridge to carry 2Å times the design load, but the extra traffic puts further pressure on the structure.

The Forth Estuary transport authority is calling for a new bridge to be built that would carry trams, cars, lorries and a light rail link similar to that found at airports such as Gatwick, which would be built adjacent to the existing bridge.

Previous Scottish Office studies have examined the possibilities of constructing a tunnel, including one built west of the existing bridge, or alternatively a tunnel made out of pre-cast concrete which could be sunk into the river bed beside the present bridge. A tunnel would cost about £800m.

Last week the Scottish National party pledged that it would fast-track a replacement for the Forth road bridge if experts concluded that a new crossing was needed.

The Scottish executive has commissioned two reports — one a survey on the condition of the bridge and a second to study a possible alternative.

Labour is keen to use its promise of a second bridge to win back those voters who switched to the Liberal Democrats in this year’s Dunfermline by-election.

“It’s a double win for Labour on this issue — we’ll be doing the right thing and also doing the popular thing,” said one insider.

Business leaders have become increasingly concerned that a decision will not be made in time to provide a new crossing before the existing bridge has to close.

Helen Eadie, Labour MSP for Dunfermline East, said that a second crossing was crucial for the economy of the north of Scotland.

“We must have a second crossing. If we don’t have a new bridge it will be catastrophic for the whole of the north of Scotland,” she said.

“We have major industries in Fife, Dundee, Perth, Inverness, right up the north of Scotland, and government has an obligation to ensure that there is a good transport infrastructure. We need to protect this route, which is vital for trade and the movement of goods.”

She added that she would prefer the choice of a tunnel because it would take considerably less time to build than a bridge, which could require 10 to 20 years. Planning for the current bridge had started in 1947 and it had opened in 1964.

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