Motorists are being warned to expect delays on State Highway 1 on the Kapiti Coast after a truck crashed into a tree.
Police said the northbound truck crossed the centre line just after 3am.
The driver was flown to hospital by helicopter with serious injuries.
SH1 at Paekakariki is open in both directions but NZTA says motorists should expect delays.
Southbound traffic was already heavy by 7am.