Chapter 1 Introduction

Transcription

1 1 Chapter 1 Introduction Figure 1.1: Westlake Plaza 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.

2 2 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

3 3 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) 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 smallscale 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 1.4: Example of City Simulation based on the idea of Fractal City (Batty, 1994)

4 4 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

5 5 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). Figure 1.6: Pedestrian activities from the book The Social Life of Small Urban Spaces (Whyte, 1980) 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.

6 6 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. 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

7 7 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.