The goal of the research presented was to create the tool that could help to define, predict and assess ex-antem sustainability of plans for development of an urban territory. The model is intended for simulation of urban development dynamics on local scale (urban municipality). The tool uses model representation of urban environment that reflects the externalities that stem out from various types of land uses and relative accessibility of each site in the represented area. The dynamics of the model is above all influenced by positive and negative externalities from uses in immediate neighborhood, spatial accessibility of the site, spatial accessibility of the infrastructure, spatial and functional constraints of spatial development declared as by-law regulatives, and transformation cost connected to change from one function to another.