chapter1 (1).pdf
TRANSCRIPT
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Chapter 1
Introduction
A warm sunny day on a downtown street and plaza, pedestrians pass on the sidewalks, people
sit on benches and steps, enjoying a cup of coffee, shoppers stroll back and forth everywhere,
children run around a strange sculpture, groups engages in conversation. The urban scene
comes alive with people activity and movement.
“People movements are one of great spectacles of urban plazas.”
(Whyte, 1980)
It is recognized that configuration of space, distribution of attraction, and social environment all
have important in pedestrian movement. However, we do not know enough about how each of
these factors individually affect pedestrian spatial behavior. The aim of this research is to look at
an urban environment as a complex system and find a way to understand and address the
dynamic process of the system that is caused by the interrelationships among all components of
the system. A set of experiments are set up as a simulation model for demonstrating our
assumption that complex behaviors in a small-scale urban environment arise from the interaction
of individuals – with the environment as well as with other individuals – following local rule.
Figure 1.1: Westlake Plaza
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Urban spaces comprise not only physical elements – buildings, streets, plazas, squares, trees,
etc. – but also the people moving and acting on them. Any single element in an urban
environment can potentially mean any number of things, depending on how it is acted upon by
other elements and how it reacts to them. How much the space is used, in part, depends on the
space's own design. But a partial influence of the design upon the use of space, which in turn,
depends on who is around to use that space and when. It also depends on uses of other spaces
beyond that space. Only a change of size of one open space or change of its configuration in
some way – separating or uniting, dispersing or mixing – may bring new sets of influence into
play, either in space itself or in its surroundings. The use of space is far more complex than a
simple problem of a ratio of an area of open space to a ratio of population. In the field of urban
design, use of space is neither static nor passive, it is dynamic; it marks the beginning and end of
each act of changing process on an urban fabric. In order to understand the dynamic quality of
urban living, we must look at the urban environment as a complex system (Jacobs, 1961) where
all parts of the system vary simultaneously in subtly interconnected ways, and in all of their
complexity are created by people (Habraken, 1998). The intimate and unceasing interaction
between people and the forms they inhabit is a fundamental and fascinating aspect of urban
spaces.
Architects and urban designers are often challenged to address the complexity in urban context.
The ideal of recursive and dynamic patterns of people and space relationships makes it difficult to
describe the value of the space. Although, the interrelations of their many factors are complex,
there are neither accidental nor irrational ways in which these factors affect each other. Jacobs
suggests the way to learn about the intricate relationships with other factors is to start at the very
detailed view, in terms of behavior of other specifics. In order to understand those complex
relationships, she has given the important habits of thought: to think about process; to work
inductively, reasoning from particulars to the general; and to seek for 'unaverage' clues involving
a very small part, which reveal way of larger and more 'average' patterns are operating.
Pedestrian dynamic movement can be examined through the lens of Complexity theory in
science. This work studies how the complexity of a system emerges in global and structural terms
from individual actions, each of which are simple and ordered in themselves. Research in
“artificial life” by Chris Langton at the Santa Fe Institute seem to be the best illustrations of the
concept of complexity and self-organized system (Figure 1.2, 1.3). Recently there has been an
increasing interest in looking at urban environments as complex systems and the notions of self
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organization are frequently used to characterize the complexity of urban environments. The
complexity of urban environments involves various aspects, but basically two can be identified.
The first is concerned with the evolution of urban structure, that is the formation of urban form
such as Fractal Cities (Batty and Longley, 1994) and temporal GIS. The second approach has
more to do with the social activities of humans within urban environments, for instance, the
pattern of pedestrian crowds and traffic flows, including the focus of this study, pedestrian
dynamic behavior.
In order to understand pedestrian behavior in relation
to other elements of urban form, space as well as the
presence of other pedestrians, one must start from the
smallest possible scale, from "a path of the feet and
the eye", as architect George Howe puts it (Thiel,
1997). This study is based on the principle that the
complexity of an urban system can be understood
through the local movement of individuals, resulting
from an interaction of an individual's visual perception
and motivation, as well as the social interaction among
individuals. There are, of course, many systems that
cannot be characterized in this way but local
movement patterns and spatial behaviors in small-
scale built environment appear to fit the approach
rather well. Local movements, in this context, are
heavily influenced by idiosyncratic factors such as
physical obstructions around which pedestrians must
navigate and immediate response to attractions.
Figure 1.2: Chris Langton’s Emergence diagram illustrating the concept of complexity (Langton, 1995)
Figure 1.3: Emergent Property: A circular mill of army ants (Langton, 1995)
Figure 1.4: Example of City Simulation based on the idea of Fractal City (Batty, 1994)
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In addition, local movement must account for different varieties of behaviors, ranging from
purposive movements to more random and exploratory ones (Batty, 1998).
The need for a much richer theory of local movement accounting for individual behaviors which
determine pedestrian acts and moves suggests that all components of environment within which
such behavior takes place as well as the individual generating such behavior must be
represented explicitly as distinct objects (Axelrod, 1997). Due to developments in programming
technology, object-oriented approaches to simulation have recently become popular. To develop
models of such local behavior, the idea of agent or individual-based modeling, where all
components of the system are explicitly represented as agents, each of whom employs rules to
determine its own behavior, seems helpful in understanding the complexity of urban
environments.
As a result, for our proposed experiment, we implement the
models as individual-based simulation, written in Java, an
object-oriented programming language. The project is called
"Mouse.class" because it appears to be the most significant
object (class, in Java, indicates a distinct object within which
behavior is encapsulated) in this conceptual experiment. We
decided to call an individuals "agent mouse" rather than a
pedestrian due to the fact that the range of behavior we model
has not yet reached a higher cognition level and thinking
process as how humans actually behave. It is our intention to
begin developing our model of behavior from the lower level
rule that represents only action execution, rising up to the
motivation level representing action selection process. This
range of behavior although (some might say) less intelligent,
proves to be more important for our emphasis on local
interactions among the components of environment. We, then,
integrate a theoretical approach as well as empirical findings
on pedestrian spatial behavior and social behaviors into an
operational model of behavior at the individual level, activating
each agent (mouse) to perform actions according to their local
rules. Through simulation one might start to think about what
actually happens in urban environment (Figure 1.5).
FIGURE 1.5: Simulation scenes from Mouse.class project
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Motivation and Objective
The motivation of this project initially comes from two sources. First is the film and book, "The
social life of small urban spaces" by William H. Whyte and his colleagues involved in The Street
Life Project (Whyte, 1980). The aim of the research project was to study how people use plaza;
people's activities in relation to elements in small public spaces, documenting extensively the
ingredients necessary for a successful pedestrian environment. We are intrigued by the way they
did the observation, using time-lapse cameras overlooking the plazas and recorded daily patterns
of use (The time-lapse camera seems to be an ideal device for studying people's behavior in
public space).
The observation is based on the principle that the movement and activity of each pedestrian in a
small place is essential to the social success of a larger urban environment, a better quality of
urban living. Using the video, the research team watched people to study their actions in relation
to physical elements as well to other pedestrians in small public spaces. Focusing attention on
each individual, the researchers then evaluated the use of space by tracing their moves – minute
by minute study of pedestrian behavior.
Figure 1.6: Pedestrian activities from the book “The Social Life of Small Urban Spaces” (Whyte, 1980)
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The second inspiration comes from the Chinese
traditional toy "Mouse Palace" (Figure 1.7). It is
a set of nicely crafted wooden house-like blocks
that children can move around and create a
place for a mouse. When they put the mouse in,
the children can observe how the mouse reacts
with the space they create. The concept is to
foster an ability to see and understand the
relationship of behavior and environment. This
kind of ability is important for architects and
urban designers to design better places for
people. Architect Don Miles, who once worked
with William Whyte, points out that what has
been missing from the study of architecture are
lessons to train eye so to see and understand
the use of space in relation to people (talk in a
Design Machine Group lab lunch event, 2001).
By combining these two concepts: 1) to understand the use of space through local movement and
individual interaction, and 2) playing is learning; this thesis describes a simulation model as a toy
or game that allows users to create a parallel world – a 2-D virtual environment – to understand
how the real urban environment actually works. In the system, an agent "mouse" carries a
pedestrian behavior – with ability to see and move, and some degree of motivations – and objects
created in "mouse environment" that imitate some characteristics of elements normally found in
a real urban environment. In other word, a mouse in the present experiments stands for a
pedestrian.
Organization of this Document
This thesis document is outlined as follows.
Chapter 2 introduces the study and related research works on individual behavior and local
movement in urban environments. The last part of this chapter explains the range of behaviors
modeled in this research. Basically, there are two types, individual behavior and social behavior.
While the first type contributes to the understanding of local movement and interaction between
Figure 1.7: Mouse Palace, a Thai-Chinese traditional toy for a child to learn about behavior and environment relationship while playing with mice, food, and wooden blocks.
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individuals and configuration of space, the second mainly contributes to the understanding of
social consequences in space.
Chapter 3 introduces the individual-based simulation, describing its definition, characteristic,
background and application, including related areas and related work. Then we review the
structure of our proposed system.
Chapter 4 introduces all the elements and their characters that are used to construct a simulation
scene to represent the environment.
Chapter 5 starts with the structure of an agent “Mouse”, outlining the key principles for movement
which are built into the model. These movements, we believe, are borne out through our
observations, causal knowledge, and theoretical studies of how people behave in small-scale
urban environments. The individual behaviors are characterized and ordered following the
hierarchy of reflex, reactive and motivated behaviors. We then present two social behavior
models, imitate and inductive of behavior, that we wish to demonstrate in the experiment. The
computable form (algorithm) of each behavior will also be discussed. These are behavioral rule
sets for each agent. The system not only represents pedestrian behavior, but there are also some
other objects that represent physical elements – blocks –, and attraction – cheese –, in space.
Each of those objects composed in the simulation will have their own characteristics as well.
Chapter 6 presents the experiments, which consist of two series. The first is the study showing
the pattern of movement based on individual behavior, to see how those individuals interact with
elements in space according to their visual perception and motivation. The second is the study on
how dynamic behavior can emerge from the interaction of individuals through simple social
actions.
The complete presentation and interactive simulation are included at the end of this document in
the accompanying CD ROM.