The design and reconstruction of transport networks remain crucial in planning processes for urban systems. Construction and reconstruction of urban infrastructure have to be planned adequately to save future travel times, construction and maintenance costs. Therefore, sound and reliable methods are required for designing or expanding transport infrastructure. So far literature focuses on optimization of existing networks. Our work contributes to the smaller field of network design using shape grammars.
Shape grammars describe with rules how network elements of different types are joined with each other. Shape grammars provide a solid foundation for coherent transport network design, and simultaneously reduce complexity of planning processes. Compared to some existing network optimization methods, transport network shape grammars require low computational requirements and are flexible and adaptive in their application possibilities. However, only a few contributions are found in standards for network design, mainly without any fundamental research basis. Therefore, shape grammars remain vague and the standards lack of clear recommendations.
In the current research work, different hierarchical shape grammars are investigated and compared against each other. A network design method is responsible for the actual transport network design and concurrently implements the shape grammars under consideration. The shape grammars are applied in different network design examples for testing purposes. The design examples are built on empty featureless planes to avoid a bias in the results. The different network design examples are compared against each other regarding an objective function. The results show that hierarchical shape grammars significantly affect transport network performance. Additionally, the results show that the proposed underlying network design method also adapts to terrain constraints. We continue examining more shape grammars to find relevant grammars for transport network design and to derive clear recommendations for urban planners.
Image: The coherent transport network proposed by the shape grammars and the design algorithm, implementing three link types (link width) and intersection types.
Reference: Vitins, Basil J.; Schüssler, Nadine; Axhausen, Kay W, (2011): Shape Grammars for Hierarchical Transport Network Design. Paper presented at the 11th Swiss Transport Research Conference, Ascona, May 2011.