Reading some wild traffic statistics from New Zealand

Only 6% of crashes in New Zealand involve foreign drivers, according to the latest figures provided by the Ministry of Transport.

But in some remote regions of the South Island particularly popular with tourists for their scenery... foreign drivers are involved in about a quarter of all crashes.

These sentences come from a CNN article about a vigilante movement in those regions popular with tourists. The vigilantes snatch car keys from tourists who annoy them by holding up traffic along the scenic routes. 

My friend Tonny saw this article and thought about Numbers Rule Your World. I love to hear stories about how you're able to relate the stories in my book to other real-world situations.

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The 6% aggregate number hides the effect of tourists on the rate of accidents. The effect of tourists is different depending on which region one is looking at. For this particular article, only the 25% number is relevant--and even this point is not clearcut. I'd like to know whether the vigilante incidents are exclusively occurring in those "remote regions of the South Island", as implied.

The 25% figure does not address the more important question of whether locals or tourists are more likely to get into accidents in those regions. While the tourists accounted for one out of four accidents, they also comprise a large proportion of the traffic. If, say, 50% of the cars on those roads are driven by tourists, then they are disproportionately less likely to be involved in accidents. The base rate of tourist traffic is the missing data.

Further, a margin of error is useful, especially if few accidents occur in those remote areas.

Chapter 1 of Numbers Rule Your World deals with the notion of the statistical average and Chapter 3 investigates when it is appropriate to aggregate data and when it's not. Learn more about the book here. 

 

Comments

[Ken]

I saw a figure from Australia that tourists are 10 times at risk of death as locals. We have some factors that don't apply to NZ like long distances and the risk of running into large native animals, although both have accidents with horses and cattle. In NZ hire cars regularly have accidents where cars leave the road but fortunately without major injuries.

What is significant in NZ is a large number of Chinese visitors. Having travelled behind one group I suspect that the driver had very little driving experience and had quite likely never passed a license test. It is an unfortunate aspect of many countries that passing tests is an inconvenience which is best avoided by paying a bribe. Most countries in Asia have abysmal mortality rates for road users.

I suspect that we should not be allowing drivers from some countries to use an international license, but it is based on commercial reasons that we don't want to deter students and tourists and in most cases they only hurt themselves.

[junkcharts]

Ken: On the analytical front, it would be interesting to see if the growth of tourists (or Asian/Chinese tourists) is correlated with the growth of accidents. Also, I suspect that any similar areas frequented by tourists will face similar statistics so establishing whether this area of NZ is unique requires better analysis.

[Catherine]

Regarding this:
"...a vigilante movement in those regions popular with tourists. The vigilantes snatch car keys from tourists who annoy them by holding up traffic along the scenic routes"

This is a misrepresentation of what is happening. The 'vigilantes' are taking keys from tourist drivers who display appallingly bad and/or dangerous driving such as repeatedly crossing the centreline, dangerous overtaking, stopping and taking photographs in the middle of the highway on a blind corner, etc. It is NOT because locals are stuck behind slow drivers, and has been quite specifically targeting really bad driving, often evidenced through dashboard cams. It tends to happen in areas where the intervention of Police might take some time so locals take action to protect other road users.

Based on my experience of driving in a country where I have to drive 'on the other side of the road' I know how easy it is to pull out and drive on the wrong side. This is far less likely to happen in a city where there are other cars to follow, but in the country it's very easy to forget, and drive for some time on the wrong side before realising. Head-on crashes for this reason are not uncommon. Bad driving is a different story and seems to be particularly problematic with Asian/ Chinese tourists but whether this is a statistical reality or a media bias is hard to tell.