Environmental Engineering Reference
In-Depth Information
achieved by increasing residential density will not be as great as initially
conceived because services and amenities will have to be augmented to
accommodate the increased population [43].
There are a number of advantages from increasing densities, which can be
summarised as follows [43]:
1. It can help protect agricultural land from urbanisation.
2. It results in less depletion of the natural resources needed for con-
struction purposes [53].
3. Built forms that facilitate higher net densities may result in signifi-
cant reductions in energy demands [15,54]. Energy use within build-
ings can be reduced by passive solar architecture, superior insulation
and energy-saving technology [54] or by built forms with low-surface
areas and combined heat/cooling and power systems [55]. Owens [15]
notes that very different densities (ranging from 37 to 250 dwelling
units per hectare) are attainable using combined heat and power sys-
tems, depending on discount rates and fuel prices.
4. Decreased pollution from vehicle exhausts can be achieved as a result
of a decline in the use of cars, the mixing of land uses, the provision
of efficient and accessible public transportation, and walking [15,54].
High densities have been found to be associated with lower gasoline
consumption per capita [35,56]; however, this is a controversial issue
[28,52,57].
5. Decreased emission of pollutants may result from energy-saving
land-use plans and from energy-efficient buildings [53].
6. High density may result in a decrease in the total number of car
trips [53]. Nasar found lower automobile dependency scores in high-
versus low-density neighbourhoods [58]. These differences were greater
for older people, women and households with no children. A decrease
in the number of kilometres per trip may also result [54,59-61].
7. High density has been found to be related to a higher proportion of
travel on public transit, to greater public transit service provision per
person and to transit use by a higher proportion of workers [20,35].
Increased public transit use, in turn, may reduce pollution emissions
(an environmental advantage).
8. High density enhances the opportunity to use public transporta-
tion because high density brings the development of public trans-
portation systems to the thresholds of profitability and efficiency.
The report prepared by Berridge Lewinberg Greenberg, Ltd. adopts
several benchmarks for the relationship between residential density
and transit use. It suggests that 17-75 dwelling units per net hect-
are are necessary to sustain significant transit use, and 150 dwell-
ing units result in a modal split of different transportation types in
which more than 50% are public transit [62].
