A crash and a separate truck breakdown in the Horokiwi area caused the delays. While the crash was cleared a couple of hours ago, the broken-down truck was not cleared until just after 10am.
NZTA regional performance manager Mark Owen said there was a truck and trailer unit breakdown, then a few minutes later a crash involving three cars and a motorbike.
Adding to the disastrous traffic, Metlink Wellington said the Days Bay ferry sailing at 9.10am has been cancelled because of bad weather.
Drivers have been calling into the Tim Fookes Morning Show on Newstalk ZB to question why the broken-down truck has not been moved from the highway, three hours later.
"I really would like some answers to what our infrastructure managers and police are doing with the highly complex problem of moving a truck," one caller said.
"These events are becoming more and more frequent, and if we keep responding to them in the same way, I think there's a clinical diagnosis for insanity.
"I just think it's time that these people were accountable. 150,000 people have been inconvenienced because we can't move a truck."
Because of the size of the truck, the specialist heavy haulage vehicle was needed to remove it.
Owen said there was the difficulty first in getting the equipment to the breakdown, then removing the truck in peak traffic.
One woman said she'd left home at 7.45am to catch a 10am flight from Wellington airport, but an hour later she was still stuck in Lower Hutt.
Another woman said she'd spent an hour coming over the Wainuiomata hill, and was trying to reach Petone where she was due to take a client for a driving test at 10.15am.
Traffic is also said to be backed up towards Eastbourne.
Maori Party co-leader Marama Fox is also one of those stuck in traffic.
Fox left home at 6am to head to an Oranga Tamariki Select Committee, but three-and-a-half hours later was still on the highway.
"I haven't even seen this truck that everybody's talking about," she said as she crawled through traffic near Petone station.
Fox said part of the problem was the sets of traffic lights along the highway, which she said should be replaced with flyovers.
The Wellington City Council said on Twitter rubbish and recycling collections would be approximately two hours later than usual because of the traffic disruption.