Breakdowns blocking two lanes on the Auckland Harbour Bridge which caused traffic to back up to Penrose this afternoon have now been cleared.

Waka Kotahi said road users should allow for extra time due to the blockages, which had occurred on northbound lanes one and five.

Traffic was backed up as far south as Penrose. According to Google, it was taking about 50 minutes to travel 12km from Ellerslie to the harbour bridge.

While both breakdowns have now been cleared, northbound motorists still face significant delays.

Meanwhile, a multi-vehicle crash on eastbound lanes on SH16 has closed the Te Atatu Rd on-ramp.

Emergency services were called to the crash at 1.31pm. A motorcyclist suffered serious injuries.

A motorcyclist has suffered serious injuries as a result of a multi-vehicle crash at the Te Atatu off-ramp. Photo / Hayden Woodward

The agency is also encouraging motorists to use an alternative route to the Te Atatu Rd on-ramp after the crash, however, a police spokesperson said the ramp was expected to reopen at 4pm.