UrbanSim is a software-based simulation model for integrated planning and analysis of urban development, incorporating the interactions among land use, transportation, and public policy. For example, a region might be evaluating two proposed alternatives for dealing with a congested freeway: expanding the freeway or building a new rail system. These decisions are often contentious and politically charged. UrbanSim can be used to help inform the discussion by simulating the long-term effects of these choices on land use, transportation utilization, and the environment. The HCI aspects of the system, in particular around public participation, have been strongly informed by Value Sensitive Design theory and methodology. The system is in operational use by planning organizations in the regions around Detroit, Houston, Salt Lake City, and Seattle; there are also experimental deployments for many other cities in both the U.S., Europe, and elsewhere. UrbanSim is open source and is available for download via the project website.