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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  1. Wow interesting data! So how many billions have we spent on new roads in the past 5 years only to see per capita travel decrease?

  2. The Auckland figures don’t agree with the ones here (http://monitorauckland.arc.govt.nz/transport/transport-patterns/vehicle-kilometres-travelled-vkt.cfm) which are sourced from Ministry of Transport. The local road figures are pretty close, but the state highway figures are much lower than at the link. The figures at the link show a solid 10% growth in Auckland state highway kilometers between 2006/7 and 2009/10. That’s surprising given the economic conditions over most of that period.

    There was a reasonably significant drop just before 2006. It seems to have been reflected nationally (http://www.mfe.govt.nz/environmental-reporting/transport/vehicle-km-travelled/total-vkt/) where total kilometers travelled increased from 26 million in 1990 to 40 million in 2007. MFE attributes the 2006 drop to fuel prices, but then explains that growth bounced back after the increased price was “normalised”, which I take to mean drivers got used to them and returned to their normal driving patterns.

    1. That’s a really interesting article, especially as they look at “trips” in total rather than trips by mode. So people visit other peoples houses less often, tend to do one giant weekly shop rather than multiple smaller shop visits, more women work rather than spend the day making household and child related trips, and we’re buying more stuff off the internet.

      1. The FT had a couple of articles on car culture recently. One on young American’s and car ownership:
        Tony Dutzik, senior policy analyst at the Frontier Group and co-author of the study, said: “The economy does have a fairly significant impact on driving. We know that young people . . . who work, tend to drive more miles per year than people who don’t.”

        But he added that “even among young people who did have jobs, the amount of miles they were driving each year was falling”. The study also found that young people with incomes above $70,000 doubled their use of public transport and bikes between 2001 and 2009.

        And another observing wider trends:
        Underlying the US trend is a change in where people are choosing to live – in city centres. And it is not just the young. “Many baby boomers, who no longer need multi-room houses and backyards (because their children have moved out), have begun moving to homes that are smaller and in locations that have easily accessible societal amenities,” the report said.

        All this may change of course, with a drop in petrol prices or widespread use of cars powered by electricity or shale gas. But if the fall in driving endures, the implications will be far-reaching – for property developers, city planners and national and local governments, who will face a heightened demand for public transport just as tax revenues from cars and petrol fall. There is far more to this than home delivery of the weekly shop.

  3. really interesting post! Considering we have spent so much money on more roads but not seen increased growth, does this impact on the theory of induced demand?

  4. really interesting post! Considering we have spent so much money on more roads but not seen increased growth, does this impact on the theory of induced demand?

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