ENGINEERS and surviving builders of the Forth Road Bridge will tonight celebrate its 50th anniversary, as figures reveal it has carried more than three-quarters of a billion vehicles.
Bridge traffic levels have fallen over the past three years but the 760 million total up to July reflects the fact it is handling twice its design capacity.
The figure has been calculated using annual bridge records, but the real total could be far higher as they are incomplete.
Since tolls were abolished six years ago, traffic has been recorded using weight sensors embedded in the carriageways as vehicles drive over them.
However, they have been out of action for months at a time, and have been bypassed during roadworks.
Virtually all the 23 million vehicles a year using the bridge are due to switch to the new Queensferry Crossing when it is completed in December 2016.
The adjacent replacement bridge was ordered by ministers because of concern about the long-term strength of the Forth Road Bridge, as its main cables have been weakened by corrosion.
That will leave the existing bridge as a “public transport corridor”, carrying buses, taxis, pedestrians and cyclists.
Farm vehicles and motorcycles under 50cc will also be permitted because they will be banned from the Queensferry Crossing, which is to be a motorway. Learner drivers will be unable to use either crossing.
However, there is expected to be pressure on the Scottish Government to ease the restrictions if traffic starts to increase again and the Queensferry Crossing becomes a bottleneck.
It will have only two lanes in each direction – the same as its older neighbour. There are also likely to be questions about the cost of maintaining the Forth Road Bridge once its annual traffic has shrunk from millions of vehicles to a few thousand.
The move will give bridge officials the opportunity to carry out major repairs which have been postponed because of the significant disruption they would otherwise have caused. They include replacing expansion joints in the bridge deck.
Sustainable transport campaigners Transform Scotland urged ministers to stick to their guns over the “old” bridge.
Director Colin Howden said: “The case for the second Forth road bridge was made on the basis that it was a replacement for the original bridge, which was misleadingly portrayed as being beyond repair.
“The old bridge must now, as has been repeatedly promised by the Scottish ministers, be kept solely for the use of public transport.”
The Forth Estuary Transport Authority (Feta), which runs the bridge, said tonight’s dinner at the National Museum of Scotland was to thank those most closely connected with the crossing.
Those attending include some of the 50 surviving bridge builders and several staff who have worked on the bridge for more than 25 years. Celebrations for the rest of Feta’s 71 staff have been put off until after the Forth Bridges Festival concludes with a torchlit procession and fireworks display on 13 September.
A total of 2,014 torch bearers will create a half-mile long “river of fire” as they cross the bridge to go a concert and ceilidh in South Queensferry featuring Big Country.