Per capita travel by car vs public transport in Australia's eight capital cities (data source: BITRE)

There’s a mountain of evidence from many western countries showing passenger travel by car is approaching, or at, saturation. In some countries it has stopped growing and in others is declining.

As the exhibit shows, per capita travel aggregated across Australia’s eight capital cities shows a slowing in the rate of growth from around 1990 and a marked decline since around 2003-04.

This might seem odd at first glance because there still seem to be plenty of reasons to drive. Cars are considerably cheaper than they were in the 70s, GDP has grown substantially over this period, we have more money on average to spend, and more places to go to.

Many reasons have been put forward to explain this change. The most popular are higher petrol prices and the GFC. While these undoubtedly have a significant effect, the slowing in travel set in before these influences. Something else is also going on here.

There isn’t a consensus around a definitive explanation, but there are many other prospective reasons for the decline, including (some of these are important and some are arguable -see previous discussions, here and here):

  • Higher levels of traffic congestion and slower average speeds – it’s too hard nowadays to travel long distances within our capital cities
  • Better public transport services – most cities enjoy improved service frequencies, a longer span of hours, and in some cities extended networks. The superior level of service has attracted travellers away from cars
  • More people live at higher densities in accessible locations – cars aren’t essential and parking is in any event too expensive or too hard to find
  • The number of jobs has grown much faster in the city centre than in the past – public transport is at its most competitive in the centre and driving is unattractive because of congestion and high parking charges
  • Greater awareness of the negative environmental implications of car travel and the health benefits of active travel modes
  • The population is getting older – retired people tend to drive fewer kilometres
  • Greater reliance on electronic communication – there is more scope to work and conduct personal business, shopping and social networking from home. Home offers more entertainment options than in the past
  • Driving costs more – although cars are cheaper to buy, insurance is expensive for young drivers, drink-driving penalties are severe, and obtaining a driver’s licence is both arduous and expensive
  • Cheap air travel – more time is spent on overseas holidays and business trips and hence not driving at home. Travellers now routinely fly rather than drive between distant destinations like Brisbane-Sydney or Adelaide-Melbourne.
  • Young people stay longer in full-time education – they don’t have the funds to buy and operate a car. More are living in urban areas where public transport is available
  • Less emphasis on cars as coming-of-age symbols – changing mores mean there’s little demand for the ‘shaggin wagon’
  • Slowing in the growth of female workforce participation – the dramatic growth of the last 40 years, which increased travel, has slowed
  • Shopping centres – larger, more diverse centres with longer-lasting perishables mean fewer shopping trips are necessary

The simplest explanation in my view is that nothing keeps growing forever. Per capita car travel in Australia grew dramatically from 1950 to 1980, but eventually we ran out of new reasons to keep increasing the distances we drive. I suspect the low cost of car purchase means just about everyone who wants a car can now get one, either new or second-hand.

That doesn’t explain the fall in per capita kilometres, though. I think a lot of the factors on the list probably contribute, but my guess is the most important one is traffic. I don’t mean congestion in the sense of gridlock, but rather in the sense that more cars on the road means slower speeds and hence shorter distances, even in the traditional non-peak periods.

Congestion has increased in part because car ownership has grown vigorously, aided in large measure by falling real prices. But it’s also because, as cities have expanded outward, more dwelling growth now takes place within established areas than used to be the case in the past. For more and more of us, the fringe is just too far.

Land uses have adapted over time to the new circumstances. A lot of what people want is now located within their home region. Much of it’s generic too – there’s little point in driving any further than the nearest hard-top shopping centre because the next one will be much the same.

Still, it’s a complex phenomenon and we don’t really know the relative contribution of the various factors. It’s also important to note that while per capita car travel is trending down, total car kilometres aren’t – they stayed at around 146 billion kilometres p.a. across the eight capitals over the three years up to 2008-09. Population growth is offsetting the fall in per capita travel, so don’t expect any short-term respite from traffic congestion .