Transport authorities say an urban freeway will close completely for the first time in recent memory to allow for construction of New Zealand's first "smart motorway".
Wellington's State Highway 1 will be closed between Thorndon and Ngauranga on Saturday night.
The New Zealand Transport Authority (NZTA) has advised motorists to avoid the stretch of motorway, which would be closed for several hours overnight.
The NZTA said the roads would stay open north of the Ngauranga Interchange on both SH1 and SH2.
The motorway would be closed in the northbound direction after 10pm Saturday until 10am Sunday morning.
This was because the old Kaiwharawhara off-ramp was being connected to the Thorndon Overbridge as part of a new northbound lane.
Southbound lanes will be closed between Ngauranga and the Aotea off-ramp for up to eight hours between 10pm and 6am as two new overhead fixed-sign gantries were lifted into place.
"If you're heading north from the city on Sunday morning, bear in mind you'll need to use the Hutt Road if you're travelling before 10am, and this will take longer than your usual trip on the motorway. If you can, please your journey until after 10am, when the motorway will be completely reopened," acting highways manager Mark Owen said.
"If in doubt, just remember the electronic signs will tell you what to do."
Mr Owen said this was the first of a series of eight motorway closures required as part of the "smart motorway" project. "Apart from the first closure, which includes connecting an old off-ramp to the Thorndon Overbridge, all the closures are to allow the overhead gantry structures, which hold either fixed or electronic signs, to be craned in and out," he said.
"The remaining closures will happen between mid-September and early October at dates still to be confirmed," he added.
The smart motorway will start operating between Johnsonville and the Terrace Tunnel early next year.
A full list of closures and detour maps was available at www.nzta.govt.nz/smartmotorway.
However, the NZTA said severe weather or other "unforeseen circumstances" could delay some closures so people should also check the Agency's Facebook and Twitter pages for updates.