Environment and Planning B: Urban Analytics and City Science

In this paper we present a perspective on approaches to enhancing the feeling of safety in the urban public realm. Many planning and urban design responses to concerns about a lack of safety in city centres seem often to have led to the ‘fortress’ city and/or the ‘panoptic’ city. These are repressive and oppressive, socially divisive and exclusive, and deny the city's inhabitants a richer urban experience. We suggest more positive ways of making city centres feel safer. We start by discussing the concept of the urban public realm, then briefly review crime and incivilities, and outline the spectres of the fortress city and the panoptic city. In the remainder of the paper we discuss positive strategies for safer city centres. By doing so, we seek to offer a resistance to the tendencies towards fortress and panoptic cities. The paper is aimed primarily at those concerned with the design and management of the urban public realm, such as local authorities, planners, urban designers, and city-centre managers. There is also a wider audience that includes retailers, city-centre property owners, the police, and others with interests in the city centre. Although many of the issues have universal applicability, the focus here is on English provincial cities.

In this paper we explore the theory and logic behind the development of the second generation of the California urban futures model, a site-specific urban growth and simulation model. The second-generation model remedies three of the major shortcomings of the first generation. It substitutes a statistical model of urban land-use change, calibrated against historical experience, for an uncalibrated ‘developer-driven’ model. It includes multiple urban land uses (for example, single-family residential, apartments, retail and office, and industrial) and allows them to bid against each other for preferred sites. It allows previously developed sites to be redeveloped into different uses. Finally, in addition to simulating the spatial impacts of regulatory policies, it can also simulate the effects of major infrastructure investments such as highways and transit lines.

If a ‘general theory of planning’ is impossible, a contingent framework is proposed to integrate prevailing and emergent planning paradigms which present four different views of planning: deliberative rationality, communicative practice, coordinative planning, and frame setting. These are not mutually exclusive but are complementary aspects of a contingent and dynamic planning process. Rationality is invoked in deliberative problem solving by individuals or quasi-individuals, whose interaction takes the form of communicative practice. Coordinative planning represents interaction between organizations, whereas the domain of planning as frame setting is the community. This contingent framework also subsumes descriptive and normative planning models, which are reviewed and illustrated.

In this paper the empirical findings and basic frameworks used in the evaluation of GIS are reviewed. In the studies reviewed, a variety of evaluation criteria are employed, but they still contribute sporadic, unsystematic, and inconclusive evidence. Going beyond a discussion about the need for measuring GIS impacts, and an uncritical and unselective adoption of computerized tools, I emphasize here the importance of assessment and feedback for better adaptation of GIS technology to the needs of urban planning. Comprehensive, multidimensional, context-based, and process-based evaluations can contribute valuable information to guide the developments in GIS technology and to facilitate efforts in GIS implementation in public and private organizations.

In this paper we propose and illustrate analytic techniques for the analysis of plans. Two issues are addressed: first, the characterization of individual surfaces according to the local and global patterns of visual connectivity between surfaces; second, the pattern of the smallest set of positions from which all surfaces become completely visible.

Liveable, endurable, and governable cities are sustained by a delicate balance of laws and policies that protect the interests of individuals, households, and firms at the same time as meeting the collective consumption needs of existing and future citizens. A general equilibrium model is developed in order to articulate some of the important theoretical features of this problem of urban management. Central to the model is the idea that sustainable policies and actions have themselves to be sustainable and that this is possible only if they reflect the preferences of citizens. Starting from a household utility-maximisation problem the model yields an equilibrium urban public goods matrix, designated the urban management matrix Γ*, which may be viewed as a socially efficient urban management objective function. It contains quantities of environmental goods, social infrastructure, and regulative services that are socially optimal in the sense that any deviation from them will make some citizens worse off. These are used to derive a set of urban system performance indicators that represent a realistic specification of a sustainable city from the current perspective of citizens. The degree of environmental sustainability implicit in the indicators depends on the preferences of existing citizens for prudent collective action. The indicators represent the optimal prescription of sustainable-city policies for present application. If pro-sustainability education and propaganda are successful in changing preferences over time, then a comparative static use of the model charts a socially and politically sustainable path towards longer term environmental sustainability. The essay is a theoretical one intended to explore the nature of collective and individual consumption trade-offs in a sustainable city.

Post-Fordist urban growth is characterised by ever-increasing dispersal and polycentricity. The transformation of urban spatial structure has profound implications for sustainable development. There is now a substantial literature both on confirming the existence of polycentricity through equilibrium and evolutionary theories and on empirical identification of subcentres. However, more research is needed to explore the generically polycentric urban growth. A microscopic simulation approach is thus applied to study how stable subcentres, measured in terms of population density, can be established. In this study, an experiment carried out in an artificial cellular city is reported. One innovative feature of this simulation is that the state of the cellular automaton comprises a quantity variable (population density) as well as a binary state variable (selected or not selected). The two are interlinked through the evolution of the city. The experiment suggests that the combined forces of accumulative population density and local interactions can lead to the formation of stable subcentres. In such a regime, subcentres are first established through stochastic ‘errors’, for example, clusters of local developments. Thereafter the clusters continue to capture development opportunities through reinforced local interactions. With the evolution, however, disutilities, such as congestion, are accumulated from the concentration of local development. The growth of disutilities changes the relative attractiveness between formed (sub)centres and other areas. When significant disutilities are accumulated, another stochastic change may overturn the dominance of (sub)centres and drive developments to other locations. The subcentre formation is validated under the general discussion of ‘goodness of fit’ of possible urban automata, and population density surfaces are measured through various ‘signatures’.

In this paper an activity-based travel-demand model called AMOS is described. The model system is capable of simulating changes in individual activity and travel behavior that may be brought about by a change in the transportation system. These simulations may then be used to predict the impacts of various transportation policies on regionwide travel characteristics. A rule-based activity-scheduling algorithm is at the heart of AMOS. The algorithm simulates changes in activity and travel patterns while recognizing the presence of constraints under which travelers make decisions. Operationally, the algorithm reads the baseline activity and travel pattern of an individual and then determines the most probable adjustments that the individual may make in response to a transportation policy. In this paper, the scheduling algorithm is described in detail and sample results from a case study in the Washington, DC metropolitan area are provided.

Rectangulations include packings of rectangles in two dimensions and packings of cuboids (3-rectangles) in three dimensions. Spatial layouts of this type are used in architectural and engineering design. In this paper we examine the spatial relations between the lines, planes, and volume elements in these designs. It is shown how to describe rectangulations as shapes in product algebras. Spatial relations, particularly adjacencies between areas, volumes, maximal planes, or maximal lines are used to represent rectangulations. More general properties of these spatial relations are derived. Generative properties of rectangulations are established which distinguish those 3-rectangulations which have an essentially two-dimensional character.