A major part of Auckland's motorway network slowed to a crawl after a truck hit the Penrose overbridge.
A digger arm hit the overbridge early this afternoon and while all lanes are now open, the New Zealand Transport Agency said motorists should expect delays.
The St Marks, Ellerslie and Greenlane off-ramps southbound have been closed to reduce the volume of traffic coming onto the motorway.
The tail of traffic is back to Fanshawe Street in the city.
There are no reported injuries and no other vehicles involved.
The last similar incident caused massive traffic disruption.
A truck and trailer hit the Penrose overbridge on March 18, flipping the trailer and blocking all the southbound lanes.
State Highway One south-bound ground to a halt, while rubberneckers slowing to catch a glimpse of the crash scene caused traffic jams on the north-bound route.
The agency says the bridge is the lowest on the Auckland network, and there are several warnings to motorists about the height limit of 4.57 metres, but it plans to upgrade them.