Class 5
Urban Form and Transportation Sustainability
Ref: Low and Gleeson, Making Urban Transportation Sustainable, Palgrave MacMillan, pg. 25 - 41.
Charts and Tables from the Newman and Kenworthy study can be viewed by
click on the link below
Global Comparison Charts
Introduction
The chapter for this class is by Peter Newman and Jeff
Kenworthy who became well known in the 1990s for a
study which looked at urban form, transportation and
energy use in a wide cross-section of cities from
around the globe.
In a more recent article, Newman argues against what
he refers to as the simple (I would say simplistic) view
of transportation that states that mobility increases with
wealth. And often that mobility is equated with car use;
therefore, more wealth equals more car use.
Newman says that the main idea in his article is that the
future of car use cannot be determined based simply on
projecting trends. He says that we need to understand
how transportation is affected by the form of cities and
the social values which sustain these cities. These
words of Newman echo such farsighted visionaries
from the 50’ and 60s as Mumford and Plowden who
where lonely voices back then in questioning our rush
to build a society that is so dependent on automobiles.
Newman believes that the guiding question for urban
development is whether or not we are making the city
more autodependent. His definition of autodependency
is interesting. He considers a city autodependent if a
thirty minute average journey to work is attainable only
by car.
Why thirty minutes? Well the thirty minutes is derived
from the idea that there is a travel time budget for
travel to work that has remained essentially constant
throughout the course of history. This constant travel
time budget is about 30 minutes and is some times
referred to as the Marchette Constant.
This constant explains why the form of cities has
changed so radically as transportation technology has
evolved. For example, cities based on walking typically
extend no more that 5 – 8 kilometers from the center,
cities based on transit may go out 20 to 30 kilometers
with the shape determined by the specific nature of the
transit, and cities based on the automobile may extend
out more that 50 kilometers in all direction. This
supports Alex Marshall’s contention that the city is
shaped by the transportation system and that the auto
scatters development over the countryside.
Newman points out that ‘sustainability’ is part of a new
paradigm in setting the direction for technological and
social interaction. Sustainability is ultimately about
network thinking as it integrates natural, financial and
social capital.
In other words, our value system is changing and so is
our attitude towards technology including
transportation. These changes are being accelerated
as we bump up against the limits of our autodependent
cities. The basic problem is that it is no longer
possible to satisfy the 30 minute travel time budget in
our sprawling urban centers. The additional problem is
that the roads and highways have reached there
carrying capacity and there is no socially acceptable
way to expand them further.
Newman reminds us that for the same space the
capacity of different types of transportation technology
is as follows: highways carry 2,500 person/hour/lane,
buses carry 7,000 person/hour, and trains carry 50,000
persons/hour.
He fails to mention walking which is by far the most
space efficient means of transportation.
Newman argues that these time-space limitations mean
that emerging, dense 3rd World cities are unlikely to
become as car dependent as 20th Century American
cities. Another limiting factor on these emerging cities
is cheap fossil fuel which has feed the growth of
autodependent cities over the last 60 years. We are
unlikely to have cheap fossil fuel going forward into the
next few decades. Therefore, Newman sees a
convergence of factors leading us away from
autodependency.
In Newman’s optimistic outlook he does not necessarily
see this as a problem as he points out that fuel use (and
auto use) is not necessarily related to wealth. He
points to a number of Wealthy European and Asia cities
where per capita energy use is relatively low.
His view is that we can build cities that are more
livable, more efficient and that satisfy the time budget
constraints. Cities like Phoenix and Houston are much
more exposed to future shocks because of their basic
make-up requires huge quantities of energy. One of
the changes that he sees that is needed is for cities to
re-concentrate. He points to Sydney and Melbourne as
cities that are well on the way to re-structuring
themselves along these lines.