Published: Thursday, 21st February, 2008 09:30
'Mini-bridges' plan unveiled
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PLANS are in hand to create ‘mini-bridges’ on the Forth Road Bridge in a bid to to reduce the impact of major roadworks next year.
Two ramps, each at least 80 metres long, will be positioned over the roadway near the bridge’s towers.
Work on rebuilding worn-out expansion joints will carry on under the ramps while traffic continues to flow overhead.
A 30mph speed limit will imposed and all vehicles except HGVs will use the ramps.
However, week-long contraflows will still be needed at the beginning and end of the project when the ramps are constructed and dismantled.
Although similar restrictions will be needed the following year when the joints on the opposite carriageway are replaced, at least six weeks of continuous contraflow will be avoided each year.
Without the ramps, a continuous contraflow of at least eight weeks would be needed to replace the main expansion joints, resulting in unprecedented traffic disruption.
Barry Colford, chief engineer and bridgemaster, said, “These joints have reached the end of their design life and need to be replaced. However, eight weeks of continuous contraflow on the Forth Road Bridge would bring almost intolerable pressure to bear on the transport network.
“We’ve worked up the design of these ramps and carried out the calculations, and we’ve now confirmed that this is technically possible.”
He added that some strengthening of the bridge deck would be required.
Forth Estuary Transport Authority (Feta) convener Councillor Tony Martin added, “These ramps will add significantly to the cost of replacing the main expansion joints. However, recent economic studies indicate that this is good value for money compared to the delays and costs to business of a continuous eight-week contraflow.”
The Feta board will discuss the proposals tomorrow (Friday).
Meanwhile, a flood prevention expert, Professor David Crichton, has called for a causeway to be built across the Forth instead of a new bridge to protect residents from the growing risk of “rising sea levels” and a “storm surge”.
He explained, “A causeway with flood gates would be cheaper, safer to build and more useful to Scotland. It would reduce the coastal and fluvial flood risk for the more than 6000 low-lying homes in the area.”
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