A truck rolling on an on-ramp is the latest in a series of crashes on Auckland's motorways this morning.

The northbound truck collided with a car and rolled on the Takanini on-ramp to the Southern Motorway just after 11am.

Neither driver was seriously injured.

The truck was leaking oil, and the New Zealand Transport Agency said the on-ramp was unlikely to reopen until about 2pm.

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The rolled truck was carrying scrap metal, a northern police spokesman said.

The truck driver suffered a shoulder injury, police said.

Earlier, about 10.50am, there was a three-car crash on the southern side of the Auckland Harbour Bridge. No one was injured.

And at about 10.30am one person was injured when up to four vehicles crashed near Papakura.

St John ambulance transferred one person with minor injuries to Middlemore Hospital.

The crash closed all northbound lanes and one southbound lane on the Southern Motorway between Takanini and Papakura.

One northbound lane and all southbound lanes have since reopened, the New Zealand Transport Agency said.

Northbound traffic was advised to avoid the area if possible or get off the motorway at the Drury or Papakura exits and travel along Great South Rd.

Police are also responding to reports that a car has crashed into a lightpole on the motorway between Beach Rd and Great South Rd in Drury.

No one appeared to be injured.

Police are on their way, the spokesman said.