It is expected that the closed section of the A83 Tarbet to Campbeltown road at the Rest and Be Thankful will reopen before the rush hour tomorrow evening.
The road was closed yesterday morning after yet another landslide hit the pass.
But trunk road contractors Bear Scotland opened up the Old Military Road as a diversion at around 3pm yesterday.
A spokeswoman for the agency today said: “Good progress is being made to remove what is now estimated to be in excess of 2,000 tonnes of material, which came down the hillside adjacent to the A83 trunk road at the Rest and be Thankful in yesterday’s landslide.
“The clearance operation involves three large specialist excavators, including a long reach excavator that was specially transported from Ayrshire overnight to extract the 1,200 tonnes of debris that was caught by the debris fencing on the hillside.
“This is the largest recorded landslide in the area. The previous worst was in September 2009 when around 1,000 tonnes of material came down the slope.”
She added that the Old Military Road diversion would remain in operation while the clearance work was undertaken.
She said: “It is expected that the A83 will reopen to motorists before tomorrow’s evening peak.
“As a precautionary measure, the road will reopen under temporary traffic signal control.”