Environment and Planning B: Urban Analytics and City Science

A computer simulation of land development subject to constraints is reported for the case of London. The study begins at a time when the ancient street system of the city enclosed blocks of open land which were developed only at the edges adjacent to the street. Despite a large subsequent increase in population, 16th-century building was constrained by a series of proclamations and laws which encouraged covert development within the block, accessed by narrow passages. The historical process of development is interpreted in terms of a set of rules governing the evolution of passageway access within the internal segments of the blocks, and the relationship between new buildings and plots. A product initially of historical research and analysis, the development rules were revised and reformulated by the man — machine interaction until the computer-generated developments were consistent with those observed in historical records. It was found that the original rules did not give sufficient weight to the street system which was of paramount importance in the spatial structure of the City: the maintenance of access to and from the street is seen as a crucial factor in the spatial evolution of London. The rules governing this particular development were considerably clarified by the computer simulation.

The application of sequential planning to the design process is discussed, considering design as a search through a space of states which are acted upon by transformation rules. Various approaches to goal satisfaction are considered, including forward inference, regression, the satisfaction of implicit goals, and metaplanning. These issues are illustrated with an example from a simple design domain. The example has been implemented in PROLOG.

Design is regarded here as the generation of a language of designs from a grammar. We consider the application of context sensitive grammars to design. Meaning in design is equated with purposeful design activity where mechanisms are devised for finding states which match goals. Regression is discussed as a tool for goal satisfaction using context sensitive grammars. Some of the complexities of implementation introduced by contextual considerations are handled by hierarchical planning. The ideas are demonstrated by means of an example where the artifact is a simple building form which is to fit into a site context. The example has been implemented in PROLOG.

A radically new approach to facility layout optimization involving nonconvex quadratic assignment problems is presented. The approach uses a simulated annealing technique originally developed to solve problems in statistical mechanics by Metropolis et al, and recently applied to VLSI chip design problems. The Metropolis algorithm is relatively simple to apply and a microcomputer model called TOPMET has been developed. TOPMET is shown to produce superior solutions to some of the more popular computer-planning techniques and hand-generated methods. The algorithm also lends itself readily to user interaction and colour graphics display, and its application is illustrated by a practical building problem. Extensions into artificial intelligence are discussed.

In this paper are reported the incorporation of (a) a selective reallocation capability and (b) a conditional reallocation capability into the LUPLAN land-use planning package. A selective reallocation capability allows the user to nominate a change of plan on part of the planning area and to view the implications of that change in policy-achievement terms prior to accepting the nominated change. A conditional reallocation capability allows the user to nominate the type of small change being sought in the plan and to learn whether any changes of that type are feasible.

The incorporation of safety considerations into land-development control decisions associated with nonnuclear hazardous installations in a major metropolitan planning authority area in the United Kingdom is examined. The experience of the case-study authority over the last ten years is examined with reference to the operation of the consultation procedure whereby advice on safety issues is obtained from the Health and Safety Executive, and with reference to the impact that consideration of safety has had on land-use around hazardous sites. Evidence is presented of serious difficulties in planning for nonnuclear major hazard installations and of problems with past and existing consultation procedures. A further aim of the paper is to draw wider conclusions in relation to difficulties in land-use planning around hazardous installations in general. Topical and controversial planning considerations are raised within an empirical context.

Most current models of spatial interaction are structured so that a change to an existing spatial alternative or the introduction of a new alternative will not change the ratio of flows from any constrained origin to any pair of unchanged destination alternatives. This recently identified weakness may cause minor problems when small changes occur in cases where the distribution of origins and destinations is relatively homogeneous. However, where facilities are not distributed uniformly and spatial substitution or agglomeration effects are observed to occur, this restrictive property, known as IIA (independence from irrelevant alternatives), can cause the models to produce counterintuitive results. In this paper this limitation is overcome using an information-theoretic approach, where additional information is provided on the entropy of aggregated alternatives which best capture any hierarchical elements in the spatial choice process. Suggestions are made on model structures suited to different forecasting applications, and the principles are illustrated by a small numerical example.