An Extensible, Modular Architecture for Simulating Urban Development, Transportation, and Environmental Impacts Michael Noth¤ Alan Borning Dept. of Computer Science & Engineering, University of Washington, Box 352350, Seattle, Washington 98195, fnoth,
[email protected] Paul Waddell Evans School of Public Affairs, University of Washington, Box 353055, Seattle, Washington 98195,
[email protected] ¤ Corresponding author Preprint submitted to Elsevier Science 5 September 2001 Abstract UrbanSim simulates the development of urban areas, including land use, trans- portation, and environmental impacts, over periods of twenty or more years. Its purpose is to aid urban planners, residents, and elected officials in evaluating the long-term results of alternate plans, particularly as they relate to such issues as housing, business and economic development, sprawl, open space, traffic conges- tion, and resource consumption. From a software perspective, it is a large, complex, system, with heavy demands for excellent space efficiency and support for software evolution. It consists of a collection of models that represent different urban actors and processes, an object store that holds the state of the simulated urban environ- ment, a model coordinator that schedules models to run and notifies them when data of interest has changed, and a translation and aggregation layer that performs a range of data conversions to mediate between the object store and the models. The paper concludes with a discussion of the lessons learned regarding software architecture to support rapid evolution within the field of urban simulation. 2 1 Introduction Patterns of land use and available transportation systems play a critical role in determining the economic vitality, livability, and sustainability of urban areas.