<style type="text/css"><!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--></style>UrbanSim is an open source software platform for agent-based geospatial simulation, focusing on the spatial dynamics of urban development. å Since its creation UrbanSim has been used in the official planningå processes for at least a dozen regional governments which were usedå to help allocate billions of dollars in regional investments in transportationå infrastructure.UrbanSim was first conceptualized in the late 1990's and implementedå using the Java programming language. The technology landscape forå scientific computing changed dramatically after that, and by 2005å UrbanSim was converted to Python, making heavy use of Numpy to vectorizeå calculations. By 2014, it became clear that UrbanSim should be reimplementedå again to take advantage of significant advances in the libraries availableå for scientific Python. The new version of UrbanSim, called UrbanSim2,å makes extensive use of community-supported scientific Python librarieså to reduce the amount of domain-specific customized code to a minimum.UrbanSim is an excellent case study for the power of leveraging thework of the scientific programming community as scaffolding for adomain-specific application, as opposed to building an extensive customizedå solution in each domain. Additionally, the open and participatoryå nature inherent in nearly all of the open source projects describedå here has been particularly embraced by governments, who are oftenå reticent to support large commercial institutions and balkanized andå private data formats and software tools.<style type="text/css"><!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}-->UrbanSim is an open source software platform for agent-based geospatialå simulation, focusing on the spatial dynamics of urban development. å Since its creation UrbanSim has been used in the official planningå processes for at least a dozen regional governments which were usedå to help allocate billions of dollars in regional investments in transportationå infrastructure.UrbanSim was first conceptualized in the late 1990's and implementedå using the Java programming language. The technology landscape forå scientific computing changed dramatically after that, and by 2005å UrbanSim was converted to Python, making heavy use of Numpy to vectorizeå calculations. By 2014, it became clear that UrbanSim should be reimplementedå again to take advantage of significant advances in the libraries availableå for scientific Python. The new version of UrbanSim, called UrbanSim2,å makes extensive use of community-supported scientific Python librarieså to reduce the amount of domain-specific customized code to a minimum.UrbanSim is an excellent case study for the power of leveraging thework of the scientific programming community as scaffolding for adomain-specific application, as opposed to building an extensive customizedå solution in each domain. Additionally, the open and participatoryå nature inherent in nearly all of the open source projects describedå here has been particularly embraced by governments, who are oftenå reticent to support large commercial institutions and balkanized andå private data formats and software tools.--></style>