A truck driver who jack-knifed and rolled on the southbound off-ramp to Pōkeno shortly after 2pm was taken to hospital in a critical condition.
The driver, a man in his 40s, was still trapped in the rolled truck when the Auckland Westpac Rescue Helicopter arrived.
Crewman and co-pilot Aaron Knight said it's believed he lost control of the logging truck as he came downhill towards a round-a-bout.
As a result, the truck and trailer jack-knifed then rolled by the State Highway 2 off-ramp.
The driver suffered multiple injuries, mostly to his lower body, and was taken to hospital in a critical condition, a rescue helicopter spokesman said.