Environmental Engineering Reference
In-Depth Information
above under each of these six headings are available now and do not depend on expectations
about technological innovation. Most are not expensive and encourage safer, healthier and
more community-based lifestyles. An obvious question is why these measures have not been
introduced already.
Looking in more detail at the role that urban structure has to play in the overall future of
urban transport, we see this policy area as a critical enabling element to many of the other
package components. Each of the future scenarios in the case studies utilises urban structure
to various degrees, using the strategic location of development, density, mix of use, local
neighbourhood and layout to encourage more sustainable travel patterns. Urban structure is
hence viewed as a critical element of the sustainable mobility vision, working alongside and
assisting investment in public transport, walking and cycling. Low-emission vehicles are only
used where private car and freight vehicle use is necessary or preferred. This builds on the
theory as developed over the last 30 years by a range of authors, and discussed previously.
The recent self-selection debate is seen as important insofar as highlighting the important
influence of attitudes to location and travel, and their relationship to the urban structure and
travel nexus, but again it is likely that attitudes are modified according to urban structure and
other contextual possibilities (Banister and Hickman, 2012).
Urban structure provides the means by which sustainable transport can be achieved in the
city, and the need for efficiency in terms of the space occupied, the energy used, and the
numbers of people carried. An important dimension is the space question - typically, about
a quarter of the ground-level urban area is used for car-based mobility, in the form of streets
and parking (Vasconcellos, 2001). This seems a very inefficient use of land, particularly where
land is valuable and can be employed for other uses, which can be much more supportive of
urban vitality and design aspirations. In many of the largest and rapidly developing cities this
figure decreases substantially.
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All cities were, of course, not designed for the levels of mobility
that are currently being experienced - as predicted years ago by Buchanan (Ministry of
Transport and Buchanan, 1963) - as street space is limited and there are many other uses
apart from traffic movement (e.g. as markets, social space or work space). There is an important
time element here - cities that were developed extensively before the 1950s-1980s motorisation
period (such as London) have tended to be based around public transport; those that were
developed in the motorisation age (Auckland) have reflected those aspirations in their design.
Many cities in Asia have very ineffective, often absent, land-use planning systems, hence have
very limited tools for guiding the location of development.
The sustainable mobility paradigm (Banister, 2008) promotes the case for urban spatial
structure being central in determining transport mode and distance travelled, as it links the
spatial distribution of population, jobs and other activities within the city to the pattern of
trips. Higher density cities encourage more walking and cycling to take place, particularly if
space is allocated for exclusive rights of way. This means that the available street space in
cities can be optimised for the highest number of users, giving both environmental and social
benefits. Urban structure evolves over time, often with 1-2 per cent being replaced each year,
through new construction and the replacement of existing buildings (Banister, 2005). In
addition, there is an increasing amount of refurbishment taking place, as the reuse of existing
buildings (e.g. warehouses and industrial buildings) can result in much greater change over a
much shorter period of time. Many cities in developing countries are also growing rapidly,
mainly driven by inward migration, and so it is important to provide homes and jobs for
