A Technical Modeler's Interface for UrbanSim, a System for Integrated. Land Use, Transportation, and Environmental Modeling

Patterns of land use and available transportation systems play a critical role in determining the economic vitality, livability, and sustainability of urban areas. Transportation interacts strongly with land use. For example, automobile-oriented development induces demand for more roads and parking (which in turn induces more automobile-oriented development), while compact, pedestrian-friendly urban environments can induce more walking and demand for transit. Both land use and transportation have strong environmental effects, in particular on emissions, resource consumption, and conversion of rural to suburban or urban land. The process of planning and constructing a new light rail system or freeway, setting an urban growth boundary, changing tax policy, or modifying zoning and land use plans is often politically charged. Strong technical support can play a critical role in fostering informed civic deliberation and debate on these issues, as well as on broader issues such as sustainable, livable cities, economic vitality, social equity, and environmental preservation. We want urban planners and stakeholders to be able to consider different scenarios — packages of possible policies and investments — and then, based on these alternatives, model the resulting patterns of urban growth and redevelopment, of transportation usage, and of resource consumption and other environmental impacts, over periods of twenty or more years. UrbanSim [1, 2] is a simulation system that is intended to provide such technical support. It performs simulations of urban development, including transportation, land use, environmental impacts, and their interactions. It is written in Java, and is distributed as Open Source software. (Source code, as well as papers and reports, are available from www.urbansim.org.) UrbanSim consists of a set of interacting component models that simulate different actors or processes within the urban environment. For example, the Residential Location Choice model simulates the process of household location — of a household deciding whether to rent or buy a dwelling, what kind (detached house, townhouse, apartment, etc.), and in what part of the city. Another model is the Developer Model, which simulates the activities of real estate developers as they decide whether to develop new housing or commercial space, or redevelop existing space. To date, UrbanSim has been applied in a number of metropolitan regions, including Eugene/Springfield, Oregon; Honolulu, Hawaii; Houston, Texas; and Salt Lake City, Utah. Application to the Puget Sound region (which includes Seattle, Washington) is substantially completed. As part of the process of validating the model, we also performed a historical validation with the Eugene data, starting UrbanSim with the 1980 data, simulating until 1994, and then comparing with what actually happened.