Traffic is beginning to flow again on State Highway Two between Petone and the Ngauranga interchange.
But trains between the Hutt Valley and Wellington remain shut down.
That's after two crashes closed both the north and southbound lanes of the road for more than an hour.
A northbound car crashed into a power pole, with the driver in a serious condition.
Moments later the driver of a southbound petrol tanker lost control and crashed, spilling diesel on the road and train line.
Police have reopened a lane each way on the road, but there are significant buildups.
Motorists are being advised to use State Highway 58 as an alternative.
Photo: NZ Herald