Police said the victim is in a serious condition and that the Serious Crash Unit has been advised.
Motorists are being told to find an alternative route or to delay travel.
Auckland Transport issued an alert just before 6.30am saying Linwood Rd has been closed between Batty Rd and Charles Rd.
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"Please avoid this route or allow extra time for diversions around the closure."
FIRE CREWS ALSO AT HOUSE FIRE IN WEST AUCKLAND
Meanwhile, fire crews are also responding to a house fire on the other side of the city in the suburb of Henderson, in West Auckland.
A Fire and Emergency NZ spokesman said crews were called out to Brookwood Drive just after 6am.
"It was well alight when we arrived," he said.
A number of cars that were parked near the house were also on fire, he said.
No injuries had been reported and there was no other danger to neighbouring properties.