Bunn said the stretch of highway where the accident occurred was narrow, with little room on the side of the road. He estimated the left-hand shoulder was only about 30cm wide.
"It's not designed for pedestrians," he said.
Police inquiries, which included talking to people in the Kaihu area at the time, were ongoing.
The woman's name would be released only after next-of-kin had been notified.
Bunn said it had been a tragic few weeks on Northland roads.
"This is the fifth road death in the first 17 days of the month. Usually we average around two a month," he said.
"At the end of the day people need to take more personal responsibility for their actions.
"We are starting to see the consequences of poor decisions being made."
Bunn said the effects went well beyond the death of the person involved.
"It's the follow-on ... These people could be someone's mother, father, brother, or sister. They're someone's family and that's it."
State Highway 12 was closed for much of the night while the Serious Crash Unit carried out a thorough examination.
