The pedestrian was taken to Auckland Hospital in a serious condition.
Cordons are in place and motorists are asked to avoid the area if they can.
Auckland Transport said the road was closed between Eskdale Rd and Salisbury Rd due to a serious incident.
A detour has been set up via Eskdale Rd and Salisbury Rd in both directions.
Auckland Transport said to be prepared for some delays.
Earlier the right-hand southbound lane of the Southern Motorway was closed due to a multi-vehicle crash at the Ellerslie-Panmure Highway interchange.
Police said they were not aware of any reports of serious injuries from the crash.
The crash was cleared and all lanes opened by 12.30pm.
Meanwhile, all commuter trains in Auckland also ground to a halt because of a signal fault.
The KiwiRail signals failed at about 11.15am stopping trains across the network.
However, just before 1pm Auckland Transport said train services were resuming, and full services should be operating again by 2pm.
It said to expect some delays and cancellations as it works towards resuming normal service.
During the halt, trains which were between stations stopped on the lines, and were waiting for an update before they moved again.
Passengers who had boarded trains at Britomart Station were offloaded.
Those who were stuck on trains say they were stranded for up to an hour.
