"The truck basically T-boned her."
The woman died on the way to hospital. The Herald on Sunday understands she has a 10-year-old daughter.
Police in the Auckland region were kept busy with several crashes, including on the motorways.
In East Tamaki, three people were hurt when a bus and a van collided.
The accident happened shortly after 2pm when the vehicles collided head on at the intersection of Kilkenny Dr and Delmont Close.
The injured included the van's driver, the elderly bus driver and a teenage bus passenger.
The van's driver had to be cut free after the crash, which left the contents of the van, including a box of smashed beer bottles, spilled across the road.
He was earlier looked after by a passing off-duty doctor.
East Tamaki Heights resident Rubin Naidoo, who was mowing his lawn metres from the smash, said a doctor drove past within minutes of it happening.
She fetched a first aid kit from her car and with the help of another motorist tended to the injured van driver who appeared "pretty lifeless".
Naidoo said the elderly bus driver was visibly upset.
"He came around the bus and was almost crying. The ambulance officers were comforting him."
Senior Sergeant John Yearbury said it appeared there was a "driving issue with the van". The serious crash unit was investigating.
Last night, four people were injured after a three-car crash in Beach Haven, on Auckland's North Shore.
Earlier, a teenage driver was taken to Auckland Hospital with serious injuries after hitting a tree in Dairy Flat on Saturday morning.
As thousands of holidaymakers prepare to travel home from their long weekend break tomorrow, the New Zealand Transport Agency (NZTA) suggested people check for good tyre tread depth, and ensure lights, brakes, cooling systems, demisters, wiper blades and batteries were working.
Clean windscreens helped minimise sunstrike and the NZTA said drivers should consider keeping headlights on while on the open road..
Last year's Queen's Birthday road toll was five.
Meanwhile, temperatures in their mid-to-late teens are expected for the North Island today and tomorrow. Hawkes Bay is the place to be this weekend, with fine conditions predicted over the next two days.
Sporadic showers are forecast over the next two days in the Auckland, Coromandel and the Bay of Plenty. The Waikato and Wellington regions can expect a mix of showers and fine spells.
Heavy rain is expected to hit most of the North Island on Tuesday.