UrbanSim is an open source urban simulation system designed by Paul Waddell of the University of California, Berkeley and developed with numerous collaborators to support metropolitan land use, transportation, and environmental planning.
[14] In Europe, UrbanSim has been applied in Paris, France;[15][16][17] Brussels, Belgium; and Zurich, Switzerland with various other applications not yet documented in published papers.
[20] OPUS includes a graphical user interface, and a concise expression language to facilitate access to complex internal operations by non-programmers.
Earlier urban model systems were generally based on deterministic solution algorithms such as Spatial Interaction or Spatial Input-Output, that emphasize repeatability and uniqueness of convergence to an equilibrium, but rest on strong assumptions about behavior, such as agents having perfect information of all the alternative locations in the metropolitan area, transactions being costless, and markets being perfectly competitive.
Housing booms and busts, and the financial crisis, are relatively clear examples of market imperfections that motivate the use of less restrictive assumptions in UrbanSim.