Marshall (2005) developed the concept of characteristic structure of a street network as a characteristic set of indicators extracted from the street network through a process which he called “route structure analysis”. In this paper we propose an integrated process for street network generation and route structure analysis embedded in a parametric urban design process. The street generator is compatible with a larger system aiming at the production of parametric urban designs. The system has been built in a parametric CAD environment and encompasses a method for interactive urban design allowing for dynamic visual responsiveness to morphological change and data change. The street network generator, presented in this paper, is based on a recursive rule which subdivides rectangles within the bounding box of a site area. For each set of goal inputs a street network is generated and “complexity” and “relative connectivity” are calculated through a semiautomatic procedure.