The woman, who had critical injuries, was taken to hospital in an ambulance.
SH1 was closed at Portland Rd and Loop Rd, with local diversions in place.
SH1 OTAIKA - CRASH - 7:40AM
Due to a serious crash north of Loop Road, SH1 is CLOSED just after the intersection with SH15. For a detour use Loop Road, SH15 Otaika Valley Roadd, and SH14. Please avoid the area if possible, and expect delays. ^HJ pic.twitter.com/OPiE8ZI4bt
— Waka Kotahi NZTA Auckland & Northland (@WakaKotahiAkNth) July 28, 2018