THE DANGER ZONE: What to do about our shameful road toll?

So much has been written about this summer's road toll. Despite the messages about speed, alcohol, seatbelts, inattention etc – we still have more than twice as many deaths this summer as last.

At first glance, it would seem people aren't getting the message, and that the enforcement isn't working, and needs to be stricter. Calls such as 'take away their cars and crush them', 'increase fines and vehicle impoundments' and the like, start appearing.

Thinking about the numbers though – it's a big ask to draw any conclusions from such a small amount of data.

In statistics, there is a thing called the signal to noise ratio - like trying to pick out a distant radio station from the static. The stronger the signal gets, the less noticeable the noise. Conversely, the weaker the signal, the more the background noise overwhelms it.

In the case of road toll statistics, the signal is the assumed effectiveness of prevention measures, measured by the number of deaths, and the noise is the natural variability in the road toll.

About that natural variability - If you could imagine keeping everything the same: Same traffic volumes, same police techniques, same weather, same everything - and analysing 10 summer holiday periods, they'd all have different road tolls. This is your natural variability.

Of course, there are other variables at play as well, such as weather, length of holiday period, volume of traffic on the road, to name just a few.

Over the past 10 years, the average toll has been 15 deaths, with a minimum of six and a maximum of 25*.

In other words, the range is 19 and the average is 15. Going back to our radio station analogy, the music is drowned in static!

From a statistics point of view, that is far too noisy a signal to draw any kind of conclusion from.

It is fair to say that excessive speed, alcohol, fatigue and inattention are the main sources of crashes. However, using the numbers as a basis for enforcement techniques is more social engineering than science.

The real problem behind all the crashes must surely be driver attitude. The problem is, you can't measure attitude. You know it when you see it, but the only measurements we have are speed and alcohol level.

If we want less enforcement and less of the 1kmh tolerances, we all just need to improve our attitude. Simple as that.

Stay safe, don't make bad decisions, and the toll will come down by itself. And if that happens, the cops might start to leave you alone if you get up to 120kmh on the desert road when it's empty.

* Statistics from transport.govt.nz