There have been 297 fatalities on New Zealand's roads so far this year.

The country's road toll has been declining for years, but after a series of horror crashes it is set to soar.

After a crash north of Taupō in which four people were killed, this year's grim toll climbed to 297.

That's already above than the toll for each of the past six calendar years and there are still more than two months to go.

Of course, the population has also been growing, but the per capita road toll has also been increasing in recent years and the ratio of fatalities to vehicles on the road has flatlined after declining almost every year since 2000.

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An analysis by NZ Initiative researcher Sam Warburton that looked at crashes per kilometre driven found that the chance of a person in a car dying on the road was 41 per cent higher than it was in 2013, and 12 per cent higher than 2016.

Data from the OECD shows New Zealand roughly in the middle of the pack for countries that records a per capita road toll.

The data from 2015 has New Zealand sandwiched between Czech Republic and Hungary, but above Australia and the United Kingdom.

The Waikato region, with its large land area and many open rural roads is the deadliest in the country. In the seven years to June 2017 there were 440 fatalities on Waikato roads.

These figures are unadjusted for population or kilometres driven.

Speed and alcohol or drugs were each a factor in 28 per cent of fatal crashes in 2016.

Only "lost control" or "failed to keep left" were a cause in more fatal crashes. A crash can have more than one cause.