The Rest and Be Thankful will be closed overnight due to safety concerns with heavy rain forecast.
Motorists travelling through Glen Croe from 8pm tonight will be diverted to the Old Military Road where a convoy system will be in place.
The area will be checked in the morning to decide if the A83 Tarbet to Campbeltown road is safe to fully re-open.
A convoy system has already been in place for a few days at the Rest and Be Thankful as a precautionary measure.
With more bad weather forecast and hillside saturation levels increasing, Bear Scotland felt tonight’s closure – which might last the full weekend – would be the safest option.
The Met Office has said heavy rain will begin in the early evening with a 95% chance of rainfall throughout the night. It is expected to continue on Saturday before turning to light showers at lunchtime on Sunday.
Risk of landslides
The Rest and Be Thankful is notorious for landslides and is often closed when bad weather is forecast to ensure the safety of road users.
Work to strengthen the landslide mitigation measures in the area are continuing, with a new roadside debris catch-pit currently being constructed.
Eddie Ross, Bear Scotland’s north-west representative, said: “We’re putting road user safety first and diverting all traffic to use the Old Military Road from 8pm this evening as a safety precaution due to forecast heavy rainfall overnight and increasing saturation levels on the hillside.
“We have teams closely monitoring conditions in the area as well as the hillside above the A83, and we’ll assess the situation on Saturday morning with a view to re-opening the trunk road under convoy operation.
“However, with heavy rainfall expected throughout much of the weekend, it is likely that further use of the Old Military Road will be required, particularly at night, and the local diversion route will be retained in a state of readiness during this period.
“As ever, we thank all road users and the local community for their patience in advance while we continue with our work to address the Rest and Be Thankful.”
Further road closures
On Sunday, the A83 will be closed at Arrochar so emergency repairs can be carried out by Scottish Water.
A diversion will be in place via the A82, A85 and A819 from 9pm on Sunday until 6am on Monday.
Bear Scotland asks that road users utilise the latest travel advice available from Traffic Scotland.