A person has been killed in an Auckland motorway crash, as collisions near Harbour bridge and on SH20 caused long delays during the morning commute.

The sole occupant of a car in a single-vehicle crash on the South-Western Motorway died at the scene on Tuesday morning, police said.

Northbound lanes on State Highway 20 between Nielson Street and Hillsborough Road had reopened by 8am but long delays would ease only slowly, NZTA said.

Meanwhile, a two-truck collision on the Northern Motorway on Tuesday morning was delaying southbound traffic as lanes were cleared.