THERE is no "off-the-shelf" solution to the problem of ice gathering on the Queensferry Crossing.

That's the opinion of Transport Scotland director of roads Hugh Gillies, responding to concerns raised after the structure closed for several hours at the beginning of December because of bad weather.

Mid Scotland and Fife MSP Alex Rowley had asked for answers following the closure but the transport chief said safety had to be put first.

"The Queensferry Crossing was closed to all traffic for around four hours on Friday 4 December due to ice accumulation, which subsequently fell onto the carriageway," said Mr Gillies.

"The safety of bridge users and workers comes first, so we will close the bridge and divert the traffic in conditions that cause ice accretions to form and fall from the structure.

"Our ability to forecast ice accretion has been enhanced following observations and measurements of the conditions that caused the issue in February 2020. A bespoke system of weather sensors has been installed to monitor these conditions in real-time.

"Detailed operational procedures have been developed and tested to optimise the way we manage any similar incidents in future."

Mr Gillies said the long-term goal was to develop a solution which would prevent ice from forming on the structure.

"The better we understand the conditions that cause this issue, the greater our chances of success. Every bridge has different design details and operates in a different climate.

"Therefore, there is no off-the-shelf solution that is suitable for the Queensferry Crossing and any viable solution will be bespoke.

"A review of measures on other bridges has been undertaken to explore the options available for the Queensferry Crossing. The review indicates that whilst many methods of prevention and removal have been studied, tested and deployed, no single method or technology has been found to be completely successful in mitigating the problem or removing ice build-up.

"Internationally, bridge owners have devised monitoring and forecasting systems, which seek to give advance warning of the risk of ice forming. As a completely successful prevention or removal methodology has not been identified, currently most operators close the bridge and wait for the ice to fall."

Mr Gillies did not rule out the use of the Forth Road Bridge as an alternative if the Queensferry Crossing was forced to shut.

He added: "Other factors, such as the associated cost of the works, success of the Forth Road Bridge (FRB) as a diversion route, frequency of ice events and safety of road users will be considered as part of the decision-making process prior to any installation of a viable option for ice accretion prevention.

"The FRB is currently a dedicated public transport corridor. Any other use would be to the detriment of public transport but, in emergency situations, its use as a short-term diversion is an option.

"It was not available on 4 December due to ongoing maintenance work to replace its main expansion joints."

Mr Gillies said the work had an expected completion date of October next year and, after that, said the old bridge could be used "as an emergency diversion" should the Queensferry Crossing have to close.

Mr Rowley welcomed the response and said: "The bridge is key for the Fife and Scottish economy. We have to do everything necessary to address the issues that have seen the bridge close."