State Highway 1 has reopened between Paekakariki and Pukerua Bay after a motorcycle and car collided.
Police said the motorcyclist has serious injuries, but is awake and talking.
They said traffic was being controlled with stop-go signs in place, and motorists should expect further delays.
The Transport Agency said motorists should use the Paekakariki Hill Road if possible.
Woman dead in Far North crash
Meanwhile, a woman has died in the Far North after a crash on State Highway 10.
Police said they were called to the scene between Zidich Road and Duncan Road in Kaingaroa just after 12.30pm.
They said a woman is dead and another woman and two children from the same vehicle have been taken to hospital.
The area is down to one lane and the the Serious Crash Unit has been advised.
Crash on Kaipara Coast Highway
A car has rolled at Kaukapakapa on the Kaipara Coast Highway.
One person has been airlifted to Auckland Hospital with serious injuries.
Diversions had been in place but the road is now clear.
Two dead in crash north of Auckland
Two people were killed in a crash on Dairy Flat Highway north of Auckland early this morning.
Police said two cars collided between Bawden and Postman roads, and the two occupants of one of the cars are dead.
The single occupant of the other car was taken to hospital in a serious condition.