Resilience work to improve the Old Military Road in the Glen Croe valley in Scotland is on course to be completed by the spring, according to Transport Scotland.
The route, which snakes below the A83 in the Highlands, provides a diversion when the Rest and Be Thankful section above it becomes impassable due to landslips or flooding.
Transport Scotland said detailed ground investigations to inform the next stage of the work will get underway in April.
It confirmed Soil Engineering Geoservices has been appointed to undertake the £1.6m contract, which is expected to last around eight weeks, weather permitting.
The current project sees the construction of a new connector road from the A83 to the southern end of the Old Military Road, improving the resilience of the temporary diversion route by relocating the connector road 100 metres north to a location less susceptible to flooding.
Fiona Hyslop, cabinet secretary for transport, said: “The Scottish government remains committed to delivering a long-term solution to the landslip risks at the A83 Rest and Be Thankful.
“The announcement last June of the preferred route option for the long-term solution was a significant confirmation of our commitment to improve the route.
“The design work for this is being progressed with a view to publishing draft orders by the end of this year.
“At the same time, we are progressing our plans to increase the resilience of the temporary diversion route along the Old Military Road. The first phase of the work to realign the southern end of the route, reducing the risk of flooding, is progressing well and remains on schedule to be completed in the spring.”
She added: “The ground investigations to inform future phases of the medium-term solution are expected to start next month and we will then look to start further works later this year, subject to obtaining the necessary consent.”
Last summer, the government said a mile-long, £470m ‘debris flow shelter’ along the Rest and Be Thankful was the preferred long-term solution to protect vehicles from landslips and falling rocks.