The A83 at the Rest and Be Thankful is to be closed until the middle of this month so debris fences damaged by recent landslips can be repaired, road maintenance body Bear Scotland has announced.
The Old Military Road diversion route will be in place 24 hours a day until the work is completed.
The fences helped to prevent two major landslips caused by Storm Aiden from reaching the A83, but they sustained some damage in the process and now need to restored, reinstated and cleared of material.
Once the work is completed in the middle of the month, one lane of the A83 will be opened under traffic light control during the day while the diversion route will be used overnight.
The Old Military Road, which has also been affected by adverse weather in recent weeks and months, will remain under close review in case it also needs to be closed.
Storm Aiden, which hit the area last weekend, brought about 90mm of rain and caused serious flooding on both the A83 and the Old Military Road, which run parallel to each other through Glen Croe.
Following the landslip issues, engineers are also installing further mitigation measures on the hillside, including a debris barrier placed within the channel carved out by the falling material.
Eddie Ross, Bear Scotland’s north-west representative, said: “The Old Military Road reopened this morning following a safety inspection from our geotechnical team, and we’re intending to keep the route in use overnight.
“We’ll be closely monitoring conditions in the area throughout the day and during the hours of darkness and we’ll keep the route under close review.
“Teams are continuing with work to control the water flow, and repair and empty the debris fences to regain their full capacity following this past weekend’s wet weather.
“Engineers also continue with work to install additional mitigation measures on the hillside at the Rest.
“As ever, we thank the local community and road users for their continued patience while we do everything we can to address the ongoing situation at the Rest.”