Drivers face a 40mph speed limit on the Queensferry Crossing from Monday as the cables on the north tower of the bridge are going to be cleaned.
It's part of a trial to measure the impact of soiling on the formation of ice.
Teams of rope access technicians will abseil from the top of the 207-metre concrete tower and use soap and water to wash down the high-density polyethylene sheaths that encase the steel strands of the cables.
The work is expected to take five to six weeks to complete.
Nearly a hundred cables ranging in length from 94 to 420 metres will be cleaned, which is more than 24 kilometres in total.
The 40mph speed limit will be in force on the bridge for safety when rope access teams are working overhead.
It will be in place from Monday to Friday between around 7am and 6pm.
Since the £1.35 billion Queensferry Crossing opened in 2014, it has had to shut to traffic in adverse weather three times due to a risk of ice falling from the cables and towers.
A team of engineers led by Transport Scotland’s operating company BEAR Scotland has been investigating possible measures to mitigate or prevent the problem.
The team has identified soiling of the cables as a potential catalyst for the formation of ice.
It's now taking forward trials to test this theory.
Chris Tracey, BEAR Scotland’s Unit Bridges Manager for South East Scotland, said: "Since the Queensferry Crossing opened to traffic, dust and dirt has accumulated on the cables.
"These tiny particles may be helping ice to accrete as crystals form around them.
"The first cables were installed in 2015 and there are no records of any ice forming on them until 2019.
"By cleaning the cables on one tower we will be able to measure the impact this has.
"As part of the project, thermal cameras are being installed at the top of each tower to monitor and measure any formation of ice.
"On this occasion the cleaning will be carried out by rope access technicians, however work is also progressing on the design of a machine to carry out this task in future, should the trial prove successful.
"We appreciate that some drivers may find the reduced speed limit during the works frustrating, however this is an essential safety measure and will only be implemented when necessary."
In parallel to the trial taking place on the Queensferry Crossing, tests are also scheduled in October at the Jules Verne climatic wind tunnel, which is a research facility at the Scientific and Technical Centre for Building (CSTB) in Nantes, France.
This major research facility can replicate all kinds of weather conditions, including different atmospheric phenomena occurring simultaneously.
That will allow the team at BEAR Scotland to test the impact of cleaning and of specialised coatings and deicing compounds on a full-size section of Queensferry Crossing cable.
Chris Tracey also said: "We’ve already installed a range of sensors to measure the conditions in which ice forms.
"These trials will further improve our understanding of the process.
"The ultimate aim is to design measures to mitigate or prevent the problem."
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