Relationship between city density and petroleum consumption
What relationship is there between how we design our cities and the amount of oil that we consume? The evidence is that there is a strong relationship. The image below shows the conclusions of a study examining the relationship between the density and petroleum consumption of 32 cities.
We can see from the image above that while Sydney does much better than most North American cities in efficiency, we are much more dependent on cars and high oil consumption than essentially all major European and Asian cities.
With the closure of the two former oil refineries in Sydney at Clyde and Kurnell over the past 15 years, essentially all of this supply is imported from overseas with very little in the way of a strategic reserve in the event of a supply disruption.
We have had 75+ years of very cheap and abundant energy, meaning that we have not had to think much about having to design urban areas in energy-efficient ways. This is reflected in the design of many new suburbs compared to most older parts of Sydney that were developed pre-1945. In most of these areas, services can be obtained via walking/cycling, or by good public transportation services, often powered by locally generated electricity rather than imported oil/diesel.
Older suburbs typically had much less separation between land uses and it was not as necessary for residents of areas zoned exclusively for housing to travel by car long distances to other areas that are exclusively zoned for commerce or industry.
Will electric cars allow us to break the dependency on oil and allow us to continue to maintain our current lifestyle in sprawling cities indefinitely? Many energy experts believe this not to be the case due to the dependency on oil in their manufacturing and other activities compared to lower density forms of electric power generation (solar and wind).
Cars account for only approximately 15% of total carbon dioxide emissions and therefore only a fraction of total energy use. Exhaust from cars is one of only many environmental impacts of sprawl, others include clearing of forests, loss of agricultural land and loss of species habitat.
With oil being a finite resource and urban development being a long-term decision, it's likely that at some point in the future these are issues that we will need to think about much more than we are at the present.