The Old Military Road in Argyll will close overnight after a forecast for heavy rain.
The route has been used as an alternative to the A83 after a significant landslip at the Rest and Be Thankful on 4 August.
About 30-40mm of rain is expected to fall in the area over the next 24 hours.
As a precaution, the OMR will close between 21:00 on Thursday and 09:00 on Friday.
Heavy rain has the potential to impact on the steep channels above and below the A83 carriageway, where loose debris and material landed.
Teams are working on a programme of complex repairs on the A83 carriageway which was damaged following the landslide.
It will be fully assessed on Friday morning ahead of expected reopening.
Traffic will be diverted via the standard diversion route of the A83, A82, A85 and A819.
- Old Military Road to close overnight after further rain warning
- Longer overnight diversion for Rest and Be Thankful
Eddie Ross, of road operator Bear Scotland said: “We’re paying close attention to the forecasts in order to ensure if it is safe for us to keep the Old Military Road open for road users given the presence of loose debris in the steep channels on the hillside.
“Heavy rain is developing overnight with particularly heavy rain tomorrow morning until 9am.
“We need to put safety of road users first. We’ll continue to monitor the hillside and the conditions in the area and do all we can to open the OMR as soon as we can once the safety assessment following the heavy rain is complete.”
He added: “Argyll remains open for business and as ever we thank the local community and road users for their patience and assure them we’re working hard to get the A83 open as quickly and safely as possible.”