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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.