Photo: RNZ / Andrew McRae
Police are pleading with motorists to stop speeding and drive to the conditions.
It comes in the wake of six deaths in four separate crashes this weekend.
Three people died and two were injured after a car and light truck collided on State Highway 1 in Whangārei after 4pm on Saturday.
Around 6pm, a motorcyclist and bus collided in Mauku, near Pukekohe, killing the rider.
Another person died and four were injured in a crash on SH1 in Taupō shortly after 9pm.
Shortly after midnight on Sunday morning, a single-vehicle crash in Christchurch claimed the life of another person.
Assistant Police Commissioner of road policing Bruce O'Brien said all the deaths could have been prevented.
"Our biggest challenge is that police messages are not getting through to motorists on how to avoid crashes," O'Brien said in a statement.
"The crashes from this weekend are all under investigation so we cannot comment specifically on the causes at this stage but history tells us that it's the same factors time and time again resulting in deaths and trauma on our roads."
Police said less speed meant less harm.
Even if speed didn't cause a crash, it was the "single biggest determinant" in whether passengers survived or not.
O'Brien said science showed just decreasing speed by 1 kilometre could reduce fatal crashes by 4-6 per cent.
Wet weather in parts of the country may also have had an impact, he said.
A third of all fatal crashes saw alcohol and/or drugs as a contributing factor, O'Brien said.
"As a community we have a responsibility to ensure we drive safely at all times and do not take any unnecessary risks - getting behind the wheel after drinking, they're risks not worth taking."
Checkpoints would be a common occurrence over summer, O'Brien said, and drivers should expect to be breath tested.
"Our officers will be out in force anytime, anywhere, to deter unsafe driving behaviour and we're working together with Waka Kotahi and the Ministry of Transport on the Road to Zero campaign to prevent road deaths. But we need everybody's help.
"We are committed to ensuring that every road user arrives alive at their journey's end and those who put others at risk will be found, prosecuted and held accountable."
Police asked that anyone seeing unsafe driving behaviour report it by calling 111.