A £340,000 project to fit and upgrade crash barriers along the A85 between Oban and the south of Dunbeg could take up to four weeks.
The project will see more than 1,800m of safety barriers installed or upgraded along sections of the route from the north of Oban to the Halfway House Filling Station.
Work started last week and motorists are being warned to expect some delays. The A85 will stay open during the project but there will be temporary traffic lights.