As an open source and modular software system using highly disaggregated data for dynamic simulation, UrbanSim has been instrumental in making integrated land-use transportation modeling accessible beyond the bespoke models that characterized earlier generations. The UrbanSim model and the collaborative OPUS framework (Open Platform for Urban Simulation) that it has spawned have stimulated much original progress in this field. The object of this thematic issue of the Journal of Transport and Land Use is to report on this work and to illustrate the various ways UrbanSim has been adapted. However, this special issue is more than just a collection of progress reports. A central theme running through all the papers is that integrated land use-transportation modeling in Europe presents a series of challenges and demands not necessarily present in the United States context in which UrbanSim was developed. Thus, while the UrbanSim system can be technically adapted to European studies given the data and resources, the prevailing land-use transportation environment in Europe differs from the United States.