One of the leading officials behind the new Queensferry Crossing has said the bridge could go on being used for several decades beyond its stated lifespan.
The £1.35 billion crossing, which will open to traffic for the first time on Wednesday, is designed to be far more resilient than older crossings, with engineers able to repair components such as support cables and expansion joints individually or in sections.
Such improvements over the Forth Road Bridge means the new crossing has a design life of 120 years, but Mike Glover, the Queensferry Crossing technical director, has indicated that may be a modest estimate.
In an interview as part of a new documentary about the 1.7 mile-long bridge, Mr Glover said the bridge could last some 30 years longer than previously indicated.
He said: “The length of time this bridge will be in position will be well in excess of 120 years – 150 years.”
His estimate, given to a new BBC Radio Four documentary presented by former prime minister Gordon Brown, means the cable-stayed structure would a permanent fixture on the east coast until 2067 at the earliest.
In the documentary, Mr Glover said there were several reasons for the bridge’s potential longevity.
He explained: “The first is that the exterior of the bridge is a continuous structure – it is a box – which means the level of maintenance that is required is very minimal, unlike the trusses on the current suspension bridge.
“The second is because the individual cables that make up the cable-stay bridge each one can be replaced without the stability of the bridge being in doubt. Whereas with the suspension bridge any problem with that suspension cable means that the bridge would have to be closed.”
The documentary, Gordon Goes Forth, will air on Radio Four at 8pm.