339 An Urbanistic Design Tool Dr. D. Chitchian 1, 2 , Prof. Dr. H. Bekkering 1 1 Delft University of Technology 2 Iran University of Science and Technology Abstract The existing CAD and CAAD programs and design applications hardly support the urbanistic design activities. Although those applications are useful means to be utilized generally in design tasks, they are not suitable tools as urbanism community needs. Most existing CAD programs are based on the architectural design process and therefore not suitable for urbanistic design. The conceptual difference between architecture and urbanism necessitates developing new CAD software based on the urbanistic design process. We believe that our developed Urban-CAD system assists designers with urbanistic design activities and overcomes the limitations of the already existing CAD applications. 1 Introduction Many CAD and CAAD programs and design applications exist to assist designers with architectural and urbanistic design activities. Most CAD programs are based on an architectural design process, so the masses or walls of a building are defined according to the heartlines of the construction. Therefore the space results from the design process. But in an urbanistic design process designers start defining the space according to the heartlines of the streets and the masses (building block) are created in the remaining defined space. With respect to the limitations of the existing CAD programs we have been working on a research project to develop a CAD program that will assist the urbanistic designers with their design process. The chosen scaling method allows designers to work on their designs at various scales or abstraction levels. This permits the designer, when working at a specific scale, to manipulate only those design objects that are associated with that scale. The profile designer tool of the Urban-CAD allows designers to create sub-elements of a street, such as a green-part or a pedestrian-part, without drawing those parts in the design file. Manipulating and modifying those parts of a street will be achieved using the provided menus in this tool without changing the design file. The current version of the Urban-CAD has been developed using an advanced CAD tool, MicroStation SE from Bentley Systems (Chitchian, Sauren and Heeling 2001). Our Urban-CAD design tool, sustaining the aforementioned capabilities, provides the designers with comprehensive information, and it fully supports the urbanistic design process. 2 The Urban-CAD System The Urban-CAD system consists of several components, each of which carries a different aspect of the urban design process. This paper describes these components, their features, and the functions that they achieve. 2.1 The Architecture The architecture of the Urban-CAD system is depicted in figure 1. The system, consisting of four