Percentage of population by density in persons per Hectare (source: Spencer et al)

In an interesting paper to the Australian Transport Research Forum, researchers from SGS Economics and Planning compared the densities of six cities – Brisbane, Melbourne, Sydney, London, Vancouver and Montreal (Urban or suburban? Examining the density of Australian cities in a global context).

Andrew Spencer, Jeremy Gill and Laura Schmahmann used small-area census data (SA 1 in the case of Australian cities) for 2011 to compare the populations and urbanised areas of the cities. They used a cut-off of 4 persons per Hectare to exclude very low density development like peri urban hobby farms.

Brisbane and Melbourne have by far the lowest (population-weighted) average density in this company, with 25 and 32 persons per Hectare respectively, while Sydney has 52 p/Ha. Greater London is in another league at 97 p/Ha, although with a population of 8.2 million in 2011 it’s significantly larger than the other cities. The Canadian cities offer an interesting comparison; Vancouver’s population of 2.3 million is similar to Brisbane’s but at 65 p/H, it’s more than twice as dense. Montreal has nearly as many residents as Melbourne, but at 71 p/H it’s over double the density.

As the first exhibit shows, most residents of Australian cities live at densities of less than 60 p/Ha. Indeed, three quarters of Brisbane’s population and more than half of Melbourne’s live at the lowest density of  just 4 – 30 p/Ha. They’re well behind Canadian cities at densities above 60 p/Ha and, notwithstanding all the current angst about high-rise, above 100 p/Ha.

The authors point to a key disadvantage of ultra low densities:

Coupled with their relatively large metropolitan areas, the distribution of density in Australian cities does not appear conducive to making a viable network of mass public transit infrastructure. 

That’s a legitimate if familiar criticism. They go on to make a number of other acute observations:

  • The construction of Australia as an urban nation – particularly in popular discourse – overshadows the fact that the majority of Australia’s urban areas feature relatively low densities.
  • Despite the claim to being one of the most urbanised countries, Australian cities are, for the most part, relatively low density.
  • Sydney, Melbourne and Brisbane might be characterised as having generally low densities with pockets of high and very high density development focused in particular areas.
  • International comparison cities appear to have been less reliant upon opportunistic high density development as they have more people living in mid-range densities than Australian cities.
  • Canadian cities are significantly denser. They also feature larger proportions of their populations living at above 60 people per hectare.

The authors question the virtue of Australian cities accommodating growth by relying heavily on a combination of city centre high-rise, high density transit-oriented development around rail stations, and fringe areas. They ask:

Should planning strategies seek to provide more housing at intermediate densities, over a larger area, rather than high densities in relatively few, concentrated areas?

The importance of the “missing middle” was explained yesterday by John Daley, Brendan Coates and Trent Wiltshire from the Grattan Institute; they indicate boosting supply in middle ring suburbs is the single most important action state governments can take to improve housing affordability while minimising negative collateral impacts (Options for housing affordability: the good, the bad and the cosmetic).

What’s needed in the middle ring suburbs is mostly 2 – 3 storey in-fill terraces/town houses that provide private outdoor space at ground level for families and are in scale with the existing suburban streetscape. Governments need to look at retro-fitting transport services (e.g. buses) to connect to the main network in many of these areas.

Extent of urban areas (excludes zones with less than four people per Hectare) compared to official/administrative metropolitan boundaries