State Versus State

Australian states are very competitive, even when it comes to road safety. As a justification for the Victorian motorcycle safety levy VMAC explains that

Trends in motorcycle and pillion fatalities since 2002 have been encouraging with an average 20 per cent reduction in Victoria compared to a 31 per cent increase in fatalities for the rest of Australia.

Apparently, Victoria is better than elsewhere. But this is the type of statistic that compares the current year to a selected previous year. You can bet your mortgage that the year 2002 was a bad one for Victoria in terms of motorcycle fatalities; if you want to appear better, simply compare yourself to a point in time when you performed badly.

So what state is best? The two figures below show the number of fatalities per 100,000 registered vehicles for Australia and its major states for the period 1995-2009. The states are plotted in order of population; the additional volatility for the smaller states is to be expected since there are lower numbers of fatalities in less populous regions. The first figure includes all fatalities (including passengers, pedestrians etc) and all registered vehicles. The second figure includes only motorbike rider fatalities and registered motorcycles. The points in red are based on estimated registration numbers as there was no vehicle census in the year 2000.




There will inevitably be differences in fatality rates between different states due to differences in climatology and demographics. Fatality rates are very useful as measure of risk, but they do not provide a means to compare the effect of the states' traffic policies on road safety. For this we need a measure of improvement. One way to construct a measure is to fit a smooth curve to each individual plot, and to calculate the negative of the slope of the curve at any given time point. The measure will be negative if fatality rates are getting worse (increasing), and positive if they are getting better (decreasing).

This measure of improvement is shown for 2000-2009 in the figures below, for all vehicles and for motorbikes respectively (for motorbikes the measure has been divided by the ratio of the fatality rates so that it is roughly comparable between the figures). The most important measures of improvement are those for the current year, as they give an indication of the direction that the states are heading. The states of SA, VIC and NSW are not only improving but appear to be doing so at a faster rate than previously. Unfortunately, the states of QLD and WA have been less than successful. WA has the unenviable distinction of being the only (populous) state that has a negative improvement value for 2009, for both motorcyclists and all road users. In WA, fatality rates are not improving.

Back to the original question: what state is best? Looking at the 2009 figures, the ordering of the states is the same whether we consider all vehicles or only motorcycles, and is as follows:

1. South Australia
2. New South Wales
3. Victoria
4. Queensland
5. Western Australia

Congratulations South Australia. The improvement shown by SA in motorbike fatality rates during the last few years is unique. In 2007 there were only 8 motorbike fatalities in SA; the first (and currently the only) single figure number they recorded in the online Australian Road Death Database. The volatility of the fatality rates in SA is naturally larger than the more populous states, so it will be interesting to see if they can remain at their currently low levels. I don't know what SA is doing, but for the moment it is working.