Environmental Engineering Reference
In-Depth Information
energy consumption. Though a new suburb may be built with water sensi-
tive urban design, low water appliances and low water gardens, householders
can still waste water. People will need educational assistance to embed a con-
server lifestyle. Such assistance can be provided and there is evidence that
with targeted programs such changes can be made for long-term gains
(McKenzie-Mohr & Smith 1999).
Challenge 2: Reducing car dependence
People in cities have a fixed travel time budget of around one hour per day.
This Marchetti Constant has been found to apply in all cities and throughout
urban history (Marchetti 1994; Newman & Kenworthy 1999). People seem
to have a biological need for restorative or reflective time that is not work or
domestic activity and in history this was based around walking between
activities. It helps us to understand why old walking cities were only 5 to 8
km across as average journeys needed to be within this time band. It explains
why transit cities built around trams and trains spread out 20 to 30 km and
car-based cities spread 50 km. It also shows why we are reaching the limits of
urban sprawl as cities go beyond this distance. And why problems of obesity
and local identity are not assisted by travel time budgets being totally
absorbed by time in a car rather than time given to walking.
Time limits are emerging in cities as we see growing road rage associated
with congestion, cities turning back in from the sprawl that has character-
ised them in the past, and the rapid growth of Transit Oriented Develop-
ment (housing and commercial development within walking distance of a
railway station) as a preferred location for people to live and work so that
time can be saved in the city (Newman 2003).
Car dependence can be understood in terms of this travel time issue.
Cities which have built only car-dependent suburbs generally have slow
public transport and unprioritised walk/bike options for local transport.
This means that they cannot provide an answer to the travel time budget for
most people without the use of a car. To overcome car dependence, travel
options are required where public transport is faster than other traffic down
all main corridors, and local transport options must favour walking and
cycling for short journeys. Land use to support this means more intensive
residential and employment activity in centres along the main corridors.
These policy priorities are based on a number of ideas that have been
argued out over many years in Australia and are now reasonably accepted by
