Police say it's possible the driver is unaware of the collision. Initially, they thought a truck-and-trailer unit had struck the 22-year-old, but an examination of the vehicle showed it was not involved.
Double-fatality crashes happened on Friday and Saturday. The first, on State Highway 1 north of Paraparaumu, fatally injured Stephanie Anne Fox, 18, and Lance Kevin Reilly, 39, of Titahi Bay, Porirua.
In the second, two young Blenheim men died in a high-speed collision with a power pole near the town. They were Gary Alexander Benseman, 22, and Brian James Cooper, 23.
Tasman road policing manager Inspector Jenni Richardson said Mr Benseman was driving behind another car, and although it could not be confirmed that the vehicles were racing, "we know they have been travelling at speed and passing each other".
"What we know is this was a senseless waste of two young lives and this accident was entirely avoidable.
"I can only hope that other young drivers will get the message that they are not invincible and cars are not toys," Ms Richardson said.
Mrs Tolley described the holiday toll, with two more days left to go, as "so frustrating".
"It's so disappointing to see those numbers rise and know that all those families, many of them unnecessarily, are going through all that grief and devastation."
She and Transport Minister Gerry Brownlee earlier issued a statement describing last year's road toll of 284 as "encouraging" - but urging drivers to remain vigilant in view of the holiday deaths.
Mr Brownlee said that when NZ last had a toll so low, the population was half its present number and fewer than half a million vehicles were on the roads, compared with 3.2 million today.
"But even with this result, too many people are still dying on our roads," he added.
The national road policing manager, Superintendent Paula Rose, said she did not believe the holiday toll reflected "the genuinely and generally good driving" seen on the roads over the Christmas-New Year period.
"The bulk of the fatalities have been really extreme behaviours. Speed and exceptionally poor decision-making have certainly been factors, not in all the crashes, but the crashes on the whole were preventable."
Provisional Ministry of Transport data for 2011 indicates alcohol was a factor in 38 per cent of fatal crashes, and speed a cause of 26 per cent.
Mrs Rose said the dramatically reduced road toll meant fewer people died on the roads as a result of alcohol than in previous years "but the percentage is disturbing".
She was particularly pleased that Northland's toll had plunged to a record low of seven, compared with 22 in 2010 and 34 in 2009.
"It has had one of our highest death rates per head of population in the past and they have a difficult network.
"Like in most rural places, public transport is not freely available and you get a high incidence of drinking and driving. But I have to take my hat off to those working in the road safety partnership arena," Mrs Rose said.
Those included organisers of marae alcohol and driving programmes and Plunket child-restraint advisers.
Northland Regional Council transport chairman John Bain said road safety messages were getting through and it was common to see drivers "getting lights flashed at them and fists shaken" if they were being stupid.
