One of New Zealand's most experienced road policing officers has resigned, saying the job is taking too great a toll on his health.

Sergeant Stu Kearns has stepped down as the head of the police serious crash unit for Auckland's motorways, ending a 28-year career as a traffic cop.

He leaves his job with one simple warning to Kiwi drivers - you're not bulletproof.

The 49-year-old says he has been to more than a thousand fatal crashes, and the late-night call-outs and coping with the aftermath of horrific collisions have affected his health.

"It's not a job I'm going to miss. I'm certainly not going to miss getting calls to go out and see somebody else's tragedy unfold.

"In some ways I feel huge relief now I don't have to deal with the carnage.

"After 28 years, people can bring me a photo of a crash scene and I can tell them when and where it was. They never leave you."

Mr Kearns said New Zealand drivers thought they were "10 foot tall and bulletproof", and would keep dying on the roads unless they learned to drive more responsibly.

"It doesn't matter how good you think you are - 98 per cent of crashes are caused by drivers.

"People still have the view that crashes are accidents. There is no such thing as an accident ... It's not an act of God."

This year's road toll stood at 367 last night, compared to 384 for all of last year and 365 in 2008.

Meanwhile, a study has identified New Zealand's most dangerous stretches of highway.

The New Zealand Road Assessment Programme, or Kiwirap, aims to reduce the number of fatal crashes by assessing risky roads and ways of fixing them.

The top five roads for collective risk - the total number of fatal and serious injury crashes per kilometre - were State Highway 2 from Napier to Hastings, SH2 from Mt Maunganui to Paengaroa, SH2 from Bayview to Napier, SH22 from Drury to Pukekohe and SH1 from Paraparaumu to Levin.

The five worst roads for personal risk were SH62 from Spring Creek to Renwick in the South Island, SH37 to Waitomo, SH94 from Te Anau to Milford Sound, SH4 from Raetihi to Wanganui and SH31 from Kawhia to SH39.

Mr Kearns, who has been a traffic officer since 1982 and was a founding member of the Auckland motorcycle squad, was called out to fatal accidents at all times of the day and night during his time in charge of the serious crash unit.

"Shift work and being on call all the time has a huge impact on your health," he said.

"I developed sleeping disorders from all the times I was called out and not able to get a decent sleep.

"I've covered the full spectrum. I think I've probably seen it all.

"If I just had half a dozen to compare I could pick out the worst. But there is such a huge list.

"Definitely the worst are when kids are involved."

One of the worst cases Mr Kearns worked on was one in West Auckland in which a man kidnapped his child, slashed his throat and tried to set fire to the car to burn the child's body.

"Then the father walked out in front of a truck and spread himself across the motorway. That was particularly gruesome."

One other case had a particular impact on Mr Kearns.

In the late 90s, a teenager lost control of his car on the Northwestern Motorway and slammed into a bus, sending it hurtling over the median barrier into oncoming traffic.

"Going in the other direction from the boy were a lovely Pacific Island couple.

The woman had just given birth to a premature baby and they had been told by the Starship that the baby was not going to survive, that he was going to live only about 10 hours.

"They were advised to go home and assemble their family and that's where they were heading. The last thing going through the father's mind was that his son was about to die.

"He was killed, but the mother survived the crash. The remarkable thing was, the little baby survived."

Mr Kearns said seeing dead bodies was part of the job.

"It's very clinical when you go to a scene and see dead bodies. They're just that, dead bodies.

"But when you deal with their families and start to get a picture built up of that person, then they become more than just an object to you."