The detour was installed due to Waka Kotahi NZ Transport Agency closing a section of State Highway 85, connecting Kyeburn and Palmerston.
Waka Kotahi maintenance contract manager Jennifer McLean said a team was installing three drainage trenches on a section of highway between Morrisons and Kyeburn, near the Gold Fields Plaque car park, because it had been prone to slips.
The work was weather-dependent but was expected to be finished by September 26, she said.
Light vehicles travelling inland from Palmerston are being detoured from SH85 at Waynes, near Dunback, via Macraes Rd, Hyde-Macraes Rd and SH87 to Kyeburn, and the reverse.
The detour adds about 30 minutes to the journey.
Trucks weighing more than 44 tonne need to detour via SH1 and SH87, through Dunedin and Mosgiel, due to weight restrictions on the Hyde-Macraes Rd bridge.
