About 5.30pm the traffic jam was about 3km long, but by about 6pm the backlog was starting to clear.
New Zealand Transport Authority spokeswoman Frances Adank said the highway was being resurfaced at the site, and for the next few days motorists could expect heavier traffic in the area.
"Loops in the road surface which detect traffic volumes and automatically adjust the traffic signals have been affected by the milling [and] resurfacing, " Ms Adank said. "They will be replaced in a few days by the contractor."
The NZTA transport operations centre was manually running signals at peak hours, to ensure traffic got through, she said.
"The traffic signals will be less responsive in the off-peak hours so people might experience slightly longer delays than they are used to. We do ask people to be patient while the system is restored."
