Environmental Engineering Reference
In-Depth Information
of housing, retail space and offices within a one-quarter mile walking radius
of a light rail system. The motivation for transit-oriented development is to
improve the ills brought about by dependence on the automobile and the
mismatch that exists between old suburban patterns and the post-industrial
culture. The goal is to preserve open space and reduce automobile traffic
without necessarily increasing density. Calthorpe [73] defines average net
residential densities of urban transit-oriented developments as 44 dwell-
ing units per hectare, with densities of 62-123 units per hectare for up to
three-story apartment buildings [43,72].
2.3.2.2 Long-Distance Leisure Time Travel: Compensatory Travel?
An important question that arises from looking at the wider issue of energy
use and greenhouse gas emissions is whether, for certain income levels,
reduced local everyday travel will be compensated for by increased long-
distance leisure travel at other times. Is it the case that—for certain income
levels—the sum of 'environmental vices' is constant and that households
managing on a small everyday amount of transport create even heavier envi-
ronmental strain through, for instance, weekend trips to a cottage or long-
distance holiday trips by plane? In the professional debate, some [73] have
claimed that people living in high-density, inner-city areas will, to a larger
extent than their counterparts living in low-density areas, travel out of town
on weekends—for instance, to a cottage—in order to compensate for the lack
of access to a private garden. In addition to this 'hypothesis of compensa-
tion', others, including the Swedish mobility researcher Vilhelmson [74],
have launched a 'hypothesis of opportunity', which asserts that the time and
money people save due to shorter distance daily travel will probably be used
for long-distance leisure-time travel [11].
A study conducted in Norway suggested that the total energy use
decreases as density reaches a certain point, although the data indicate
that the total energy use increases at higher density levels. This pattern is
similar to a pattern in the relationship between energy use and city size
found by a number of empirical studies of cities in Norway, Sweden and
England [18]. According to these studies, up to a certain point, energy use
per capita decreases as density increases, but thereafter energy use starts
to increase. Thus, the advantages of 'megacities' or 'extreme density areas'
seem to be outweighed by the advantages offered by more modest forms of
urban compact ness [11].
2.3.3 Road Network and Transportation Network
Transportation is the leading consumer of energy and fuel in the city.
The spread of roads among extended urban areas has helped people eas-
ily commute within these vast areas, thus making distances irrelevant and
promoting more and more dispersion.
