Protesters are carrying flags and signs saying their rights are being breached have begun to gather.
They are demanding an end to all mandates and COVID-19 restrictions, and what they see is media censorship of their views.
More vehicles were on the highway north of Wellington.
Waikanae resident Tim Costley was travelling north of Wellington and said there were a "couple of thousand" vehicles from Ohau to Waiterere Beach which all but stopped south-bound traffic near Levin.
"They're bumper-to-bumper the whole way through to Levin, you just can't drive south on Oxford Street, the main road, at all.
"They've all got flags and signs - it's big.
Wellington City Council said commuters should avoid the CBD if they are trying to get across town by car, in case of traffic disruption, and public transport passengers should check Metlink's website for updates.
Prime Minister Jacinda Ardern Ardern told Morning Report she wouldn't be meeting protesters at Parliament.
Lockdowns meant people sacrificed some of their usual rights and abilities to keep others safe, she said.
The protest came at a time when the government was changing the way it was doing things because of the extra protection vaccines provided, she said.