Per capita trip generation rates for cars and public transport, 1900–2013 (Source: BITRE)

This exhibit prepared by the Bureau of Infrastructure, Transport and Regional Development shows the historical change in per capita number of trips by mode for all Australian capital cities. (1)

There are three ‘big’ messages here.

First, car travel is declining relative to population growth. It’s important to note though that absolute travel is still increasing; however it’s at a much more modest rate than in the past. For example, car travel grew by half a Billion kilometres between 2012 and 2013 compared to 3 Billion from 2002 to 2003.

It’s also important to note that traffic isn’t distributed uniformly in cities, so traffic congestion will continue to increase in some localities and so will the pressure on governments to “do something about it”.

Second, the use of public transport is static relative to population growth. Absolute growth is strong but off a small base. For example, heavy and light rail patronage increased by 0.1 Billion trips over 2012-13 compared to 0.08 Billion trips in 2002-03 (no change for buses).

Increases in patronage are due to a number of factors, including investment in new infrastructure, adding more services on existing infrastructure, and the turn-around in the decline of central city employment.

Third, total travel is declining relative to population growth. This is the most important message. It indicates that the fall in per capita car use is relatively independent of the change in public transport patronage; the latter doesn’t have a lot to do with it.

So why is travel by car declining relative to population growth? I’ve been discussing the reasons for this for a long time now (e.g. see here and here). There are many possible explanations, including more overseas travel (you can’t drive if you’re out of the country); it’s harder to get a driver’s license; the GFC; higher petrol prices; and more.

The key reasons though appear to be substitution of the internet for (some) trips; more time spent in education; having children at a later age; ageing population; and ‘saturation’ of travel demand e.g. the growth in women entering the workforce has slowed. (2)

The data suggests that the inexorable growth in car travel of the last century is finished; peak car has been and gone. The decline might not continue as the world economy picks up, but car use will probably grow in line with GDP rather than at the high rates of the past. (3)

That has obvious implications for the level of investment in urban roads, especially now that private investors aren’t prepared to carry much risk. Interestingly, it also means the induced demand hypothesis won’t be as compelling in all situations as it has been.

Politicians would also be wise to take note of public transport’s relatively static share; that’s a bigger question that I’ll look at separately.

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  1. The pattern is broadly similar for all capital cities – see Will we drive a whole lot more in the future?
  2. Some common explanations, like smart phones replacing the status of cars and the growth in inner city population, are marginal at best. The change appears to be manifesting as fewer trips, not shorter trips. It also seems to primarily be in non-work trips, not commutes.
  3. At least until autonomous cars are proven; it’s likely the technology would greatly increase the capacity of the road system and hence the demand for car travel in cities, even while it reduces the size of the metropolitan car fleet.