Annual per capita passenger kilometres by mode, Melbourne (data from BITRE)

Back in May I compared the historic level of passenger travel by car in Australia since 1970 against rail and bus, showing the significant flattening in car use from circa 2004-05 and the upturn in travel by public transport. This sort of long term perspective is useful for understanding the relative importance of the changes in each mode — something which isn’t as evident if only the last five or six years is examined.

The accompanying exhibit shows the change in passenger travel by mode just within Melbourne, using data from the Bureau of Infrastructure, Transport and Regional Economics (BITRE). Importantly, it also allows for the increase in population and hence shows the change in per capita passenger travel. The period is the 33 years between 1976/77 and 2008/09.

It can be seen that private – or individual – travel (i.e. car, van, motor cycle) has fallen sharply since 2004/05, by 1,236 km. Conversely, public – or shared – transport travel (i.e. train, tram, bus) increased by 301 km. While the curves are still a long way apart, it’s notable that the gap is closing primarily because Melburnians are driving less.

I haven’t seen anything which shows confidently and unambiguously where the fall-off in driving is happening. For example, is it outer or inner urban driving? Is it certain trip purposes only? Is it fewer trips? Is it shorter trips? Is it confined to particular demographics? Or is it something else entirely? As with most things, the outcome we see most likely results from the interplay of a number of factors, rather than from a single dominant force.

The usual suspects called on to explain these trends include increases in the price of petrol, in traffic congestion, in parking costs, and in the level and quality of public transport. Other explanations include the theory that baby boomers are getting older (and hence driving less) and the conjecture that the long distance drive is increasingly being replaced by cheap air fares (although this relates more to non-urban travel).

Then there’s Gen Y’s declining interest in driving, the impact of new communication technologies and growing interest in health & fitness and environmental issues. There’s also the theory we’ve hit saturation level with driving – we can drive to enough opportunities already, we don’t need more. Perhaps another reason is the increase in women’s workforce participation leaves them with less time and need for driving.

While it’s tempting to assume the decline in driving and the increase in public transport use must be connected in some way, it doesn’t necessarily follow that all of the difference, or possibly even the greater part, is directly related. For example, the saturation hypothesis can explain declining car travel, but not increasing pubic transport use. Likewise, the ageing of baby boomers doesn’t provide a ‘symmetrical’ explanation. It might be the curves are moving in opposite directions for largely (but by no means entirely) unrelated reasons.

My feeling is that slowing speeds might have something to do with why we’re driving less. It’s simply getting too hard to drive any sort of distance on a regular basis. There was a time when a trip from my place to St Kilda for dinner was a reasonable undertaking, now it seems like a major expedition! Fortunately there is an increasing number of alternative, closer, places to go. This adds to the sense that Melbourne is really a city of regions – there’re multiple “Melbournes”. But perhaps there are some trips people don’t bother making at all anymore.