Analysing Auckland’s VKT

VKT, or “vehicle kilometres traveled”, is perhaps the most accurate way to measure – in aggregate – whether traffic volumes are going up or down. It’s perhaps not quite as critical as ‘peak flows’ in determining whether and where our infrastructure is at capacity, but it gives us an overall picture that most other measurements can only hint at.

Which is why I’m really interested in the answers to a couple of written questions Labour Transport Spokesperson Phil Twyford has put to Minister Gerry Brownlee over the past few weeks. One on state highway VKT over the past five years in Auckland and one on local road VKT over the same time period. They show, with a little bit of fluctuation, pretty small annual increases in both figures: Both totals have, on average, increased by around 1% a year. But that’s not really the complete story because we would expect VKT to increase as population increases – what’s really interesting is whether each person is driving more or less each year. Using Statistics NZ population estimates for each of the past five years we can start to develop some ‘per capita’ numbers: What the table above shows is that in 2006/2007 your average Aucklander travelled 2,931 kilometres on the state highway network and 5,572 kilometres on the local road network. By 2010/2011 both numbers had dropped: state highway travel dropping by 49 kilometres per person, local road travel by 144 kilometres per person and therefore a total of 193 less kilometres travelled per person in 2010/2011 compared to 2006/2007. That’s around 3.7 kilometres less per person per week – not an insignificant number.

More important than the level of decrease is the fact that per capita travel is decreasing at all. And remember, this is only travel within Auckland so explanations such as long-distance driving shifting to air travel or people taking fewer domestic holidays probably doesn’t make as much difference in Auckland as it would elsewhere.

It would certainly be quite helpful to see whether this trend is something that started around 2006 or whether it’s a longer lasting trend. I was certainly under the impression that traffic levels have typically increased at a faster rate than population growth (obviously, until recently). If per capita travel on the roading network continues to decline in the future, that has some pretty major implications for our future transport planning – specifically that we really might not need many of the roading projects that have been justified based on an assumption that per capita travel would at least stay constant, if not continue the longer historical trend of actually increasing.

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