Energy use of compact cities

Compact cities part 4

The link between global warming and climate change, vis-à-vis the “compact”-ness of a city, which we wrote about last week, can be traced through the energy requirements of transportation. If we look at the “historic” perspective of cities, we can see that this is a new (modern) phenomenon. Man has been travelling for thousands of years by walking or using animal power. Most notable of this is the horse, from which we coined the word “horsepower.” It is only in the last century or two when we use engines to propel transportation. Engines use fuel.

We have also postulated that the “compact”-ness of the city, while influenced by urban population density, is also defined by uniformity over which the population is spread. That is the reason why it’s not advisable to use urban density measurements on wide swathes of land because the density may only be confined on a much lesser area with a lot of empty spaces without. However, in comparing cities, it is established that denser cities have much lower energy consumptions than sprawled cities.

A 1989 comparison of 32 cities showed that transport-related energy consumption declines rapidly with higher urban densities (source: UN-Habitat report 2013). It showed that 26 US cities averaging the lowest densities have twice the fuel consumption per capita than Australian cities, around four times as much as more compact European cities, and 10 times that of three compact Asian cities – Hong Kong, Singapore, and Tokyo. When graphed, the data set closely followed an x-y axes asymptotic curve of the function f(x) = 1/x (pardon the technicality). We repeat for emphasis – a resident of Hong Kong consumes only 10% of the energy required by a person is a typical US city. Energy consumption almost always translates to the CO2 emissions issue of climate change.

Why is this so? The answer lies on two interrelated concepts: 1.) Land use and transportation integration, and 2.) Transit-oriented development. Daily human activities always require mobility, and the more trips we do, the more energy we require. The other truth is the father we travel, the more energy we use. That’s why another important number is the least-talked about, often-forgotten, but more relevant, vehicle-kilometers-travelled (VKT) or vehicle-miles-travelled (VMT). The farther you travel, for the same purpose, the higher is the energy consumption. Ergo, compact cities use less energy per capita. By as much as a ratio of 1:10!

If cities decide to be compact, it would be more aspirational than actual. Cities take decades to develop their urban form, which can’t be simply be changed overnight. But there needs to be the desire and the commitment. As always, it starts with the principle, followed by the policies and decisive strategies. What are generally recognized as important are the following goals: 1.) Reduce the need for travel; 2.) Reduce travel distances; and 3.) Promote the use of public transportation, walking, and cycling. The last one arguably should be imperatively stated as to reduce dependence on private cars.