The compact city and sustainable transport: Another look at the data

The suite of policies known as the 'compact city' has emerged as the most popular prescription for reducing automobile dependence. The evidentiary base for the compact city draws on previous studies that compared population density and automobile use in a range of metropolitan areas, and that concluded that density is strongly related to automobile use. This paper re-examines the data on transport and density in US, Canadian and Australian cities, using census data on mode share for the journey to work, and on the density of 'urbanised areas'. This comparison is possible because the three countries' census agencies collect density and mode share data on a comparable basis, although the Australian and Canadian agencies only publicly released density data following their 2006 censuses. These data allow cross-city and cross-national comparisons to be performed on a more accurate basis than was possible at the time of the earlier studies. Standard statistical techniques are used to examine the relationship between density and the mode share for automobiles, public transport and walking/cycling. The relationship turns out to be different from that reported in previous studies: public transport and automobile use are only weakly correlated with density, while walking and cycling show no correlation at all. The significance of these results is discussed in light of equivalent British and European density and travel data, and some figures on centralisation of employment. The conclusion is that the effectiveness of the compact city model has been overstated, and the effectiveness of transport policy itself understated.