Two drivers were critically injured when a vehicle drove for several kilometres along the wrong side of Auckland's southern motorway early on Friday.
The police said a vehicle was driven onto the Mt Wellington off-ramp just before 1am.
They said the driver continued south before colliding head on with another vehicle travelling north next to the East Tamaki onramp.
Both drivers were taken to Middlemore Hospital with critical injuries.
The motorway was closed for several hours and reopened about 4am.
The Police Serious Crash Investigation Unit is appealing for any witnesses to come forward.