Motorists headed from Wellington to the Kāpiti Coast on State Highway 1 are being urged to delay their travel after a truck and two cars collided.
Police said there were reports of injuries following the crash, which happened in the northbound lane between Pukerua Bay and Paekakariki.
The NZ Transport Agency said the crash had been cleared, but traffic remained at a standstill in the area.
Newstalk ZB reporter Katrina Bennett was driving on Paekakariki Hill Rd, which she said was "really congested".
"Cars aren't moving quickly at all - it's heavy in both directions.