Motorway traffic is gridlocked after a flipped truck left two lanes blocked north of the Auckland Harbour Bridge this afternoon.

Queues stretch back 7km to Spaghetti Junction and spilling onto the Northwestern Motorway link north.

Motorists are being advised to expect delays on State Highway 1.

Two right-hand northbound lanes after the Onewa Rd on-ramp have been blocked by a truck left upside down following the crash.

Waka Kotahi NZ Transport Agency said motorists should expect delays and merge with care.

Police said motorists should expect long delays and allow additional time to reach their destination.

A police spokesperson said the single-vehicle crash, near the Esmonde Rd on-ramp, was reported at 1.09pm.

“One person has been transported to hospital with moderate injuries.

“Two northbound lanes are currently blocked while the scene is cleared.”

A number of North Shore buses had also been delayed by the crash.

A truck crash on Auckland's Northern Motorway has caused kilometres long queue stretching up to the Spaghetti Junction. Photo / Google Maps