A lane on State Highway 29 is blocked after a car went into a barrier near Baypark.
A police spokesman said emergency services were called to the crash about 7.20am on State Highway 29 between Truman Ln and the Maungatapu Rd on-ramp.
The eastbound lane is blocked, but there were no reports of injuries at this stage, he said.
Ambulance and fire crews were also at the scene.
A Fire and Emergency NZ spokesman said traffic control was in place.
No one had been trapped.