The Scottish Executive has launched a consultation on whether to build a tunnel or a new bridge to maintain the ‘crucial road link’ across the Forth estuary.
Transport Scotland has whittled down an original list of 65 options for replacing the 40-year-old Forth Road Bridge, which is described as ‘showing signs of deterioration’.
The executive is inviting views on options for the replacement crossing – either a tunnel or a bridge – to be built to the west of the existing, iconic structure. It says a new crossing is needed because the Forth Estuary Transport Authority must replace the road bridge’s main cables, or add new ones, which could take up to seven years, with contra-flows for 56 weeks and partial closures for 48 weeks.
The consultation highlights Transport Scotland’s conclusion that a 2.2km cable-stayed bridge would be the ‘best-performing option’ for a replacement, with the ‘highest benefit-cost ratio’, of over four to one.
It would cost an estimated £1.5bn at 2006 prices, and take five-and-a-half years to construct. But an immersed tube tunnel would be as quick to build, and would perform better environmentally, the consultation acknowledges. A bridge would have direct impacts on a Site of Special Scientific Interest on the north shore.
The Forth Tunnel Action Group, lead by civil engineer, John Carson, claimed that an immersed tube tunnel would have a better whole-life cost, if maintenance costs were considered, and would avoid closures due to high winds and fog. Alastair Andrew, Forth Estuary Transport Authority general manager, stressed the need for a multi-modal crossing, which a tunnel could not provide.
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