A woman has been taken to hospital after the car she was driving collided with a truck in the North Shore suburb of Glenfield.
Glenfield Rd, near the intersection with Coronation Rd, has been closed following the crash which was reported at 12.15pm.
Both sides of the road were affected, police said.
Southbound traffic is being diverted down Coronation Rd and northbound traffic is being turned around.
Motorists are strongly advised to avoid the area and seek alternative routes.
"Police are well aware of the severe impact the closure will generate and all efforts will be made to open a northbound lane as soon as possible," police said.