A man is in a critical condition after the truck and trailer he was driving rolled near Tongariro National Park just after midnight.
A St John Ambulance spokesperson said the driver was thrown out of the cab in the crash, at Tohunga Junction, north of Raetihi.
The badly injured driver was taken to Whanganui Hospital.
A police spokeswoman said the road was closed for six hours and the scene was still being cleared.
One lane was re-opened just before 6am.
