V. Community and Urban Systems
The spatial arrangement of buildings in communities and urban
systems can play an important role in GHG reduction.
Higher density, more spatially
compact and mixed use developments offer the potential for significant reductions in GHG emissions
through three complementary effects:
Reduced per unit area consumption of district energy for cooling, heating, and power generation;
Reduced municipal infrastructure requirements, including the reduced need for construction of
streets and electric, communication, water, and sewage lines, and other services; and
Reduced VMT, including shorter freight and person trips, as well as the substitution of these
trips with public transit, walking, and cycling.
The achievement of significant reductions, however, will require a major change in the way U.S.
urban systems have been evolving over the past half century. The well documented post World War II
flight to the suburbs by both households and businesses has created the phenomenon now known as
Enabled and encouraged by the popularity of the private automobile, inexpensive gaso
line, and an extensive high speed highway network expansion program, a key characteristic of sprawl has
been the emergence of large tracts of essentially single use land developments. This includes land given
over to detached single family homes, as well as large areas devoted to commercial strip developments
and multi store shopping centers. The resulting separation of trip origins and destinations has translated
to a significant increase in not only daily commuting distances, but also in the frequency as well as the
length of many vehicle based shopping and other personal service trips.
Between 1969 and 2001, the
average annual VMT per household increased from 12,400 to 21,500 (while average household size fell
from 3.2 to 2.6 persons, and the average number of vehicles per household grew from 1.2 to 1.9).
Towards a Climate Friendly