Motorists heading to Wellington are being warned of major delays after flooding completely closed part of State Highway 1 near Manakau.
One lane of the road between Otaki and Levin has been reopened but the transport agency says people travelling to Wellington should allow an extra hour for their drive.
There are also hold-ups on State Highway 2, as some sections of the Rimutaka Hill Road have been reduced to one lane due to slips.
NZTA regional performance manager Mark Owen said contractors were managing traffic with stop/go signs.
"It's pretty challenging, we've got two different problems on two different highways, it's great to have the police working with us as well, but obviously we want to make sure the road is safe before we allow people through."