Environmental Engineering Reference
In-Depth Information
Unparalleled mobility . . . is generally a good thing, and has probably helped to bring us
to the level of economic development that we currently enjoy . . . perhaps those in less
developed countries that aspire to similar levels of mobility are not deluded, but have put
their collective fingers on the main root of economic well-being.
(Stopher, 2004, p. 129)
Taylor (2004) similarly argues against investing in public transport as a response to congestion
difficulties, arguing that moving public transport 'back' to the mass market scale in many
cities is likely to be impossible, and that congestion or road pricing options are more beneficial.
Hence there is much debate as to future possibilities and pathways, and even as to the necessity
for any change at all.
A similar debate and scepticism occurs over links between urban form and travel. The
mainstream view is that urban form, covering various facets of development (homes, work-
places, leisure, retail and other facilities), location, design and layout, makes a large difference
to the resulting travel behaviour. The early research developed from an international city
comparative analysis on density and energy consumption in transport (Newman and Kenworthy,
1989; 1999); the general thesis being that higher densities were associated with reduced travel
distances and transport energy consumption, and this could support greater use of public
transport, walking and cycling. It was recognised that land use and travel decisions co-determine
each other, i.e. there are close linkages between the location of development, urban structure
and travel (and the reverse - that transport investment is associated with a resulting urban
form) (Wegener and Fürst, 1999; Albers, 1974). A typology of approaches (
Figure 1.25
) was
put forward, including:
•
Point structures: cities are orientated towards the central point of the urban system, usually
the core urban area, e.g. the compact city or polycentric city model;
•
Linear structures: cities built along a corridor, usually along major transport infrastructure,
e.g. Soria y Mata's linear city.
•
Area structures: low density development, lacking a clear spatial hierarchy and central
structure, e.g. Wright's Broadacre City.
A rich literature has developed, eventually covering a wide range of built environment
factors, including density, settlement size, jobs-housing balance, mix of use, the location of
development, extending into local neighbourhood and street design. All these factors are
associated with travel at various levels of significance. Different metrics of travel (by mode,
distance, energy consumption, CO2 emissions), scales of analysis, and socio-economic and
attitudinal variables have also been incorporated over time, and there is now a quite sophisti-
cated understanding of urban structure and travel relationships (including Cervero, 1989; 1996;
Banister et al., 1997; Headicar and Curtis, 1998; Ewing and Cervero, 2001; Stead, 2001;
Schwanen and Mokhtarian, 2005; Hickman et al., 2009c; Aditjandra et al., 2012). The built
environment variables have been translated into the three Ds (density, diversity and design)
(Cervero and Kockelman, 1997), five Ds (with the addition of destination accessibility and
destination to transit) (Ewing and Cervero, 2001) and even seven Ds (demand management
and demographics) (Ewing and Cervero, 2010; Hickman et al., 2010c). The 'meta analysis'
view is that destination accessibility, distance to urban centre and neighbourhood design
(intersection density and street connectivity) are the most significant built environment
variables.
