Dissecting the Streams of Planning History: Technology versus Policy through Models

arguments concerning the need to explore cities as emergent complex systems from the bottom-up. Most of the conference dealt with new approaches based on simulating systems at the fine scale using cells, agents, and networks, but most of the models presented were a far cry from those that might have any use in practical plan making. Interesting intellectually, the new generation of urban models is largely of pedagogic value, to demonstrate a way of thinking about the city rather than as tools for action. Dick Brail (2004) in a controversial paper entitled `̀ Planning support systems evolving: when the rubber hits the road'' summed up the current dilemma by saying: `̀More recent interests in CA and agent-based approaches have built on earlier work in urban simulation.When coupled to increasing powerful visualization tools these developments have fostered a number of PSS [planning support systems] implementations. The question remains, however, about how such systems will enter the planning and public policy arena. '' In fact, what is emerging is another alternative to large-scale modelling which is being culled from many of these developments in GIS, PSS, and visualisation. More modest models based on limited aims are being developed, linking diverse and often stand-alone techniques into wider PSSs. These contain different kinds of model which range from full-scale simulation to diagnostic-indicator-like approaches, often embedded within wider participatory contexts. Some of these approaches do have fully fledged models within, such as the Community-Viz Simulator (Kwartler and Bernard, 2001). A new generation of sketch-planning-type models is being developed to cater for more practical needs, where the exigencies of policy force the development of models and tools which are closely adapted to the local situation and can be developed quickly enough to give some fine tuning to the problems in hand. Many models, particularly those based on cell-space ideas, cannot be easily tuned to the local context and, until this is possible, they remain as interesting but rather theoretically orientated tools for demonstrating principles rather than for applications. After fifty years of development, urban simulation models still throw up the dilemmas of using science and new technologies in policy in ways that tend to stretch what is possible. It is as if the challenge of developing good models, which probably depends upon painstaking and continuing research and development of the normal science variety, is always forsaken for overly ambitious and often unworkable techniques which, when developed, are found wanting in some obvious and important way. Technology interacts with policy in diverse, symbiotic ways which develop tensions that get resolved by changes in culture and context as much as by adaptation of the science behind the technology or the technology itself. This implies that models once developed never really get a chance for continued development. It is as if there is no such thing as the development phase in such applied contexts, for there is never any stability to the policy context. These are important issues in developing a science of planning which is commensurate with the issues facing the future of cities in a global world. This journal is receptive to such ideas and I would welcome articles which take these arguments further.