A campaigner against drowsy driving is calling for drivers to make sure they have plenty of sleep before getting behind the wheel this holiday period.
Martin Jenkins says internationally fatigue is recognised as being just as risky as drink driving.
And in some areas of New Zealand it causes up to 50 percent of road accidents.
Martin Jenkins says drivers need to recognise the signs of fatigue and act immediately.
"Head nodding, continual blinking, yawning, can't remember the last few kilometres, missing key exits and drifting across the road," he says.
Nationally, fatigue is thought to contribute between 20 to 25 percent of crashes, but some areas are worse than others.
In south Waikato it's 40 percent, in Taupo 50 percent and in Southland 40 percent.
"I think fatigue is generally under-estimated across New Zealand," says Nelson Bays area commander Inspector Steve Greally.
Mr Jenkins says micro-sleeps of just three seconds cause a lot of head-on crashes.
And there are three times of day when we're most at risk - 7am, mid-afternoon and 2am.
"Once you fall asleep on our roads, you lose directional and speed control of your vehicle, and when you do, it's likely you're going to impact with an obstacle at the same speed you fell asleep at," says Insp Greally.
And this is what you should do about it.
Take regular breaks, swap drivers with someone who's less tired, pull over and have two strong cups of coffee then a 15 minute power nap - in that order, Jenkins says, because it takes 15 minutes for the coffee to kick in.
Or get someone to pick you up.
He says road safety campaigns focus on speed, alcohol, restraints and intersections but inattention and fatigue are being ignored.
"Every other developed nation has a 15 minute power nap message to save lives, except New Zealand," says Mr Jenkins.
One of the greatest risks is what the Australians call "get-home-itis", when drivers fall asleep in the last stage of their journey, because they're nearly home and that's when they start to relax.
Police say there will be more emphasis on the risk of fatigue in the next phase of their Safer Journeys campaign which rolls out later this year.