A man is in critical condition after being ejected from his small truck when it hit a car in Wellsford.
The incident happened on State Highway 1, near Wayby Valley Rd, just after 4pm.
Auckland Rescue Helicopter co-pilot Aaron Knight said the man in his 20s suffered head trauma, a fractured leg and collarbone.
"The occupant of the other vehicle was relatively unscathed.
"The weather was pretty treacherous in the area."
Knight said the man was treated at the scene, including being intubated, before he was airlifted to Auckland Hospital.
A St John spokeswoman said earlier this evening that an ambulance, helicopter and doctor were at the scene.
Diversions are in place at State Highway 1 and Kaipara Flats Rd and again at the intersection of State Highway 1 and 16.