IT is the showpiece road bridge which when opened four years ago was heralded by First Minister Nicola Sturgeon as "a symbol of a confident, forward-looking Scotland" and a "feat of modern engineering".

But the Queensferry Crossing has had to be shut down for two years running due to the potential danger of falling ice.

Last year it emerged that new sensors failed to give enough warning to shut the crossing connecting Edinburgh and Fife before ice fell causing potential danger to motorists.

Now it has emerged that new efforts to solve the ice fall issues had to be postponed due to equipment breakdown at the Jules Verne Climatic Wind Tunnel in Nantes.

This week will see laboratory tests carried out on potential methods of mitigating against ice build-up on the crossing, having been postponed from October.

Transport Scotland-appointed road maintenance firm Bear Scotland said that a specialised research facility will allow them to recreate the conditions that cause ice accretion and test the impact of cleaning and of specialised coatings and de-icing compounds on a full-size section of Queensferry Crossing cable.

READ MORE: Sensors again fail to stop danger to motorists from falling ice on Queensferry Crossing

Chris Tracey, Bear Scotland’s unit bridges manager for south east Scotland said:“There is no existing proven solution for preventing ice accretion, so the team has been carefully reviewing and examining a variety of possible options to determine which are worthy of further research and development.

HeraldScotland:

Queuing traffic on the A876 after the bridge was closed

"A number of options have been ruled out, however some are being taken forward for further investigations, testing and development. A peer review panel of international experts has been assembled to assist with this process.

“This is painstaking work, and it has taken until now to reach the stage where we are ready to test possible solutions.”

Since last winter, nine new optical and thermal cameras have been installed on the towers for the purpose of monitoring ice – three on each tower.

An additional nine thermal sensors have also been installed on the shortest stay cables, to detect subtle changes in surface temperature.

These are in addition to the five clusters of weather sensors installed on the bridge in 2020 and thermal sensors installed during construction as part of the bridge’s structural health monitoring system.

Mr Tracey warned: “Cameras and sensors will not prevent ice accretion; however they will improve our understanding of the issue and give us some early warning when the conditions that cause ice accretion occur.

"They will also help us to confirm forecasts and determine when it is safe to reopen the bridge.

“If conditions conducive to ice accretion are forecast, Bear Scotland staff will be mobilised to respond quickly. Ice monitoring teams will patrol and inspect the bridge and staff in the control room will closely monitor live data from the weather sensors and cameras, in consultation with expert meteorologists. We will close the bridge and divert the traffic if ice formations are observed on the tower or cables, or witnessed falling onto the carriageway.

READ MORE: Farce Road Bridge: Disbelief as Queensferry Crossing forced to shut yet again despite new ice sensors

“We don’t know when the next ice accretion event will occur, but road users can be assured that we are exploring every option for mitigating this risk and reducing the disruption caused if the Queensferry Crossing does need to close.”

This Sunday marks the anniversary of the crossing being shut to vehicular traffic in both directions after patrol staff had noticed ice falling.

HeraldScotland:

Workers clean the cables on the north tower of the Crossing 

It was the third winter in a row that falling ice had plagued the £1.35bn crossing and the second time it had been forced to shut down.

At the time, Bear Scotland said that a weather sensor system reported "conditions conducive for ice formation" several minutes before the ice fell.

But it was only after the ice had fallen that the road was shut for four hours.

A month later falling ice hit a roads maintenance vehicle.

Local MSPs in and around Fife raised concerns about the development and Scottish Conservative mid-Scotland and Fife MSP Dean Lockhart described it as a "national embarrassment".

In November, last year, as new ice sensors were installed, transport secretary Michael Matheson suggested lessons had been learnt from the previous winter's issues which saw ice fall onto cars for the second time in a year.

According to original contractor information there was already a multi-million pound real-time sensor system with 2,300 installed, which included the measuring of environmental impact. These include anemometers to measure wind, barometers, rainfall gauges, air temperature and humidity sensors.

Transport Scotland was previously criticised for lack of action after reports of ice falling on vehicles in February, last year.

Before it opened, bridge operators said the 3.5m high wind shields, would "almost entirely eliminate the need for closures".

Ice on the cables was considered as a "potential issue" during the design of the bridge, but Transport Scotland's road maintenance contractor Bear Scotland said it was expected to be a "relatively rare event" with the climate experienced at the Forth.

When the bridge was under construction in 2016, then transport secretary Derek Mackay assured the Scottish Parliament that "the decision to build in structural health monitoring as part of the new Queensferry crossing - a first for a UK bridge - is an example of the efforts that will safeguard that essential crossing for the future".