Fixing the problem of falling ice at the £1.3bn Queensferry Crossing could take years and require a “bespoke" solution, MSPs have been told.

Bridge bosses admitted extensive research and development would be needed to identify a “permanent viable solution” for the main road link between Fife and the Lothians.

In the meantime, visual inspections and closure of the crossing would remain the principal response to any more incidents this winter and next.

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The Queensferry Crossing closed last week after ice fell from overhead cables onto the carriageway damaging eight vehicles.

Drivers were forced to take a 35-mile detour via the Kincardine Bridge to cross the Firth of Forth for two days.

Holyrood’s rural economy and connectivity today quizzed Transport Secretary Michael Matheson and officials about the problem.

Mr Matheson said ice falls had happened only twice on the bridge, the first time last March and then again last week.

However the first falls had happened so quickly that engineers had been unable to identify where they had come from or how the ice formed.

Indeed, they had wrongly assumed it had fallen largely from the bridge towers, when in fact the problem was with the cables.

“They had a very limited level of knowledge of what had led to that incident occurring,” he said, adding the circumstances had been “very challenging”.

He said: “It is something which historically has been rare in its occurrence.

“There isn’t an off-the-shelf solution for bridges that experience this problem. What international experience would say is that very often they have to look at bespoke methods.

“The research is trying to identify what are the very specific circumstances and potential mitigation options and do they have to be made bespoke for the Queensferry Crossing.”

Mark Arndt, of the Amey Forth Bridge Operating Company, said the ice build-up last week was different from ice build-up on similar bridges in other countries.

He said: “The formation of ice we observed last Monday [February 10] was very different from what a lot of the other big bridges incur, where you get a slow build up of ice.

“What we saw on Monday was sleet and slush conditions which resulted in ice formation and slush on the cables and parts of the towers forming very quickly, which is dissimilar to some of our counterparts in Sweden and the like, where we’ve been liaising.”

He said there was now a three-phase plan to address the problem, but a lasting one would take time.

He said there would be “enhanced monitoring” this winter“, and in the medium term, faster traffic management measures next winter and using the old Forth Road Bridge, which the Queensferry Crossing was meant to replace, in emergencies.

He said: “We’re also actively looking for permanent viable solutions into mitigating ice forming in the first place. That will take time through research and development and the like.

“The ice sensor will also be installed by next winter.

“Then the longer term solution will be to consolidate that research and development that’s required, to introduce permanent viable solutions where appropriate to the climatic conditions and design activities of the Queensferry Crossing.”

Mr Arndt said the ice had so far formed in “a very unique set of circumstances”, but might also form in other, as yet unknown, circumstances.

Asked by Labour MSP Colin Smyth how often ice fall might happen, Mr Arndt didn’t know.

He said: “In terms of the number we expect, I couldn’t quantify that. But that enhanced monitoring regime is in place to protect the public.”

He said water-repellent cable coating or heating elements might ultimately be needed.

He said: “There’s various options we need to look at that are very specific to the design characteristics of Queensferry. That could mean coating the cable sheath in a particular hydrophobic material. It could be heating. It could be a number of different things.

“So gathering that intelligence from around the world on other bridges together with whatever modern technology systems are available, we will be engaging with a specialist research facility to do laboratory simulation on those characteristics..

“So that any solution that is taken forward to prevent ice forming on the cables are specific to the bridge characteristics at Queensferry.”

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The design for the bridge was chosen by a group of MSPs chaired by Jackson Carlaw, now the Scottish Tory leader, who last week criticised the ice problems.

Laurence Shackman, Queensferry Crossing Project Manager (Design and Construction phase) for the Scottish Government, told the committee ice build up was “considered to be a relatively rare event based on the knowledge at that particular time” during the design phase and that the Holyrood committee hadn’t considered it.

He said: “I can’t recall the bill committee actually going down to that level of details about the build up of ice in the bill process.”