The Rest and Be Thankful road has been fully reopened for a two-day trial.
It is the first time that the landslip-prone A83 route will open for over 24 hours in more than eight months.
The link road in Argyll has been shut down or partially closed since heavy rain caused a landslide of 6000 tonnes of debris in August last year.
A 48-hour operation will be held over two days to consider if the route can remain open safely overnight on a long-term basis.
The old military road will remain on standby as a local diversion route.
Teams from BEAR Scotland have been working on the programme 24/7 and hope the two day trial will help identify any potential issues associated with operating the route at all hours.
Eddie Ross, from BEAR Scotland, said: “While we’re hopeful we can safely move to 24-hour operation of the A83, we must underline that if there is wet weather forecast or a weather warning – particularly overnight – which we think could impact the hillside then we will look to use the OMR as before.
“Road user safety remains of paramount importance and we will only operate the A83 if we are content that it is safe to do so.
“Teams have been working 24/7 on the mitigation measures in the area, including strengthening the debris fences and creating a new debris catch-pit, with such features strengthening landslip resilience and providing greater protection to road users.
“As ever we thank road users and the local community for their patience while we do everything we can to address the ongoing issues at the Rest.”