Scotland’s potholes: Ageing roads battered by ‘disastrous’ freeze-thaw cycle and ‘sink plunger’ impact of traffic.
Scotland’s ageing, waterlogged roads are being pummelled by the “sink plunger” impact of traffic that is worsening potholes without the protective quilt of winter-long snow cover, roads chiefs have told The Scotsman.
As motoring groups and campaigners fear roads have deteriorated amid the coldest weather for 12 years, highways officials have explained some of the unique challenges faced by Scotland’s councils as they battle to keep their networks in shape.
The latest official figures are expected to show Scotland’s local authority-run roads, which comprise all but motorways and other trunk roads, to be in a similar condition to the last survey covering 2019-21 – but they will not take into account the freezing temperatures and high rainfall of the last three months.
The Society of Chief Officers of Transportation in Scotland (Scots), which represents council roads chiefs, said such weather was the classic cause of potholes.
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Vice chair Philip McKay, who is also head of roads and infrastructure for Aberdeenshire Council, said: “We have just come through a colder than normal winter and will probably start to see the impact of that on the road network – we have seen an uptick in reports of potholes.”
He said some areas had experienced a particularly cold two-week spell in mid-December, such as 1.8C below average in Aberdeenshire.
Mr McKay said: "That causes deep-seated freezing in the road structure followed by a ‘freeze-thaw’ cycle.
"That is fairly disastrous if the road surface has any defects in it because it allows water in, and as it freezes it expands and makes the hole bigger. Then it thaws, more water gets in and you get into a fairly vicious cycle.
"When you start to include the hydraulic effect of vehicles passing over that water, it’s almost like using a plunger in a blocked sink.
"It forces the water down under pressure and you get an aggressive attack, making the hole bigger again, and if it freezes the next night, you get that ongoing cycle.
"Quite quickly, on a heavily-trafficked road, a defect can become a pothole.”
However, Mr McKay said Scotland’s roads did not benefit from a protective “quilt” of snow blanketing them for months, unlike snowy countries such as in Scandinavia.
He said: “Their roads get a limited period of cyclical freeze and thaw while we are exposed to that an awful lot more. We try to remove snow and ice from the roads because we don’t have it cold enough for long enough.
“But If you go to Scandinavia or North America, they will tend to put ‘traction’ on top of the snow, which is going to be there for a long time, to make it safe to drive on.
"Their techniques include spraying a mix of hot water and sand, which freezes as soon as it hits the snow which essentially creates a sandpaper carpet to drive on.”
Scotland’s ageing, waterlogged roads are being pummelled by the “sink plunger” impact of traffic that is worsening potholes without the protective quilt of winter-long snow cover, roads chiefs have told The Scotsman.
As motoring groups and campaigners fear roads have deteriorated amid the coldest weather for 12 years, highways officials have explained some of the unique challenges faced by Scotland’s councils as they battle to keep their networks in shape.
The latest official figures are expected to show Scotland’s local authority-run roads, which comprise all but motorways and other trunk roads, to be in a similar condition to the last survey covering 2019-21 – but they will not take into account the freezing temperatures and high rainfall of the last three months.
The Society of Chief Officers of Transportation in Scotland (Scots), which represents council roads chiefs, said such weather was the classic cause of potholes.
You've got to be in it to win it! Enter for a chance to win this house
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Omaze
Vice chair Philip McKay, who is also head of roads and infrastructure for Aberdeenshire Council, said: “We have just come through a colder than normal winter and will probably start to see the impact of that on the road network – we have seen an uptick in reports of potholes.”
He said some areas had experienced a particularly cold two-week spell in mid-December, such as 1.8C below average in Aberdeenshire.
Mr McKay said: "That causes deep-seated freezing in the road structure followed by a ‘freeze-thaw’ cycle.
"That is fairly disastrous if the road surface has any defects in it because it allows water in, and as it freezes it expands and makes the hole bigger. Then it thaws, more water gets in and you get into a fairly vicious cycle.
"When you start to include the hydraulic effect of vehicles passing over that water, it’s almost like using a plunger in a blocked sink.
"It forces the water down under pressure and you get an aggressive attack, making the hole bigger again, and if it freezes the next night, you get that ongoing cycle.
"Quite quickly, on a heavily-trafficked road, a defect can become a pothole.”
However, Mr McKay said Scotland’s roads did not benefit from a protective “quilt” of snow blanketing them for months, unlike snowy countries such as in Scandinavia.
He said: “Their roads get a limited period of cyclical freeze and thaw while we are exposed to that an awful lot more. We try to remove snow and ice from the roads because we don’t have it cold enough for long enough.
“But If you go to Scandinavia or North America, they will tend to put ‘traction’ on top of the snow, which is going to be there for a long time, to make it safe to drive on.
"Their techniques include spraying a mix of hot water and sand, which freezes as soon as it hits the snow which essentially creates a sandpaper carpet to drive on.”
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