NZ Transport Agency Waka Kotahi says the culvert replacement work will close the northbound lane of State Highway 1 at Braeside from Monday until June 3.
A detour between East Taieri and Kinmont Park (Mosgiel interchange) will be in place as the worksite will take up half the road-width.
Southbound drivers will also be affected, with their lane down to 30kmh.
NZTA Otago and Southland journey manager Nicole Felts advised drivers to plan for delays.
"Road users should expect delays, especially northbound drivers rejoining SH87 at the controlled intersection where there will be periods of congestion.
"Airport-bound people also need to build in extra time as they head south.
"If you live within the work area you will need to head south when you leave your property then return from the north as the road will be running southbound only."
The entire project is expected to take up to eight weeks, with the detour running for the first month.
A large, 0.9m-diameter culvert is being installed near Braeside, as the existing historic culvert is no longer fit for purpose.
The detour will be like previous major roadworks in this area, with southbound traffic able to continue as normal and northbound traffic detoured off SH1 left on to Riccarton Rd, right on to Gladstone Rd South, right on to SH87 towards Mosgiel, Quarry Rd and on to the Mosgiel on-ramp to continue north on SH1.
Crews will be on site weekdays between 7am and 7pm, but the detour and speed restrictions will be in place all hours.
The footpath within and next to the site would operate as usual during this initial four-week phase, the agency said.
