Revealed: the 67 Scottish roads at risk of landslide

The A82, A83 and A9 are the roads with the biggest hazards, closely followed by the A86 and A87. Parts of the country's key arterial routes such as the A1, A7, A77, M74 and M90 are also at risk.

Transport Scotland's risk comprehensive assessments, promised more than four years ago, have been welcomed by transport and environmental organisations. But they urge the government to act on the findings, and warn that landslides will increase as pollution warms the globe.

Phil Flanders, the Scottish director of the Road Haulage Association, pointed out that the detours and delays caused by road closures put a major strain on industry. "It's a big worry for everybody if trucks can't get through because shops and factories can run out," he said.

"This has been a serious problem for years and hopefully the government will now remedy the situation."

According to Dr Richard Dixon, the director of WWF Scotland, the sight of cars stuck in landslides had become one of the most striking manifestations of the world's changing climate. "This analysis shows that most of Scotland's major tourism and commerce roads are already under threat from landslides," he said. "This threat can only get worse as the climate changes more, bringing more extreme weather across Scotland. We also need to know where landslides threaten railways, homes and offices."

Landslides are caused by a combination of heavy rain and steep slopes. When large amounts of water fall on porous sandy soils and peat, they rapidly become saturated. If they are underlain by rock or some other impermeable barrier, the water can literally liquify the ground.

On steep slopes this can trigger what geologists call a "debris flow", resulting in many tonnes of mud and rubble moving far and fast. Records suggest there have been about 175 major landslides in Scotland over the last 100 years, with an increasing number in recent decades.

As well as causing severe disruption to travel and business, sudden landslides can put motorists' lives in danger. In August 2004, major problems were caused by landslides on the A83 near Cairndow, the A9 to the north of Dunkeld and the A85 at Glen Ogle, where 57 people had to be airlifted to safety after their vehicles were trapped.

These events prompted the then Scottish Executive to launch a major investigation aimed at identifying the roads most at risk of landslides in the future. Tomorrow's report, called the Scottish Road Network Landslides Study, written by leading experts for Transport Scotland, is the result.

The report's initial assessment was that over 600 of Scotland's 3200 kilometres of roads were "potentially" vulnerable. Further studies involving geographic information systems, detailed maps and site inspections concluded that 380 kilometres of road were at serious risk.

This was broken down into a list of 67 specific sites with the "highest hazard rankings". Top of the list by a long way was the A82, which runs from Glasgow to Inverness via Fort William.

Altogether, 16 stretches of the A82 were identified as at high risk from landslides, six of them in the top ten. A 13.4-km stretch along Loch Lochy, north of Fort William, was rated as the most hazardous of all.

Other parts of the A82 at high risk included 13.5 km along north Loch Lomond, 12.9 km at Glen Dochart near Crianlarich, and sections through Glencoe and around Invermoriston on Loch Ness.

Eleven stretches of the A83 to Campbeltown were assessed as at high risk, including the approach to the Rest and Be Thankful in the Arrochar Alps. In October 2007 this road was closed after 400 tonnes of soil and stone slid down the hill.

Ten sections of the A9 from Edinburgh to Thurso were rated as hazardous. These included 21 km around Helmsdale in the far north, Glen Garry north of Pitlochry and a section north of Dunkeld.

Five stretches of the A86 from Spean Bridge to Kingussie and five stretches of the A87 to Skye were said to be at risk, as well as three sections of each of the A85, the A830 and the A835.

Three kilometres of the M90 from Edinburgh to Perth were rated at risk from landslides north of Glen Farg. So was the M74 from Glasgow to Carlisle along a small section at Elvanfoot, north of Beattock.

Other high hazard roads included the A1 between Penmanshiel and Howburn, the A7 north of Selkirk and south of Teviothead, and the A77 around Glen App in South Ayrshire.

The Transport Scotland report pointed out that major engineering solutions such as re-routing roads or constructing retaining walls were expensive and intrusive. "It is anticipated that relatively few locations would justify this kind of expenditure," it concluded.

Instead, the report suggested that more should be done to improve the public's awareness of the problem. There should be better road signs, improved weather forecasts and more road closures.

"A number of the recommendations made in this study have already been taken on board and activities are under way in key locations to manage the exposure of road users to landslide hazards," said the transport minister, Stewart Stevenson.

"I believe that continued investment in this study, its recommendations and the associated study of the broader implications of climate change on the road network will ensure that Scotland is well placed to deal effectively with landslide events in the future."

Jim Barton, Transport Scotland's chief roads engineer, argued that a safe and efficient road network was vital to Scotland's economy. "We will continue to work with our operating companies, local authorities and the police to make sure that our roads are resilient and that drivers have the best information possible when making their journey," he said.

Sheila Rainger, head of campaigns at the RAC Foundation in London said: "Now that these risk areas have been identified, the Scottish government must take measures to minimise the risk," she said.

"We want more than just signage. They need to think about drainage and if necessary re-routing roads," she added. "It is not good enough to suggest that landslides are inevitable."