Access structure

Although various hierarchical structures have been investigated with respect to the different elements of urban form, the hierarchical spatial order of access from streets to plots and buildings has not been adequately explicated and objectively assessed. In this article, a new method, access structure, is presented to bridge this knowledge gap. Based on Krop’s generic multilevel diagram of urban form, different types of access structure are developed and symbolically represented. They are then quantitatively measured and compared using three metrics and an associated ternary diagram. Subsequently, the new method is tested first in analysing the internal structure of an individual urban block and then in distinguishing urban blocks with different structural characteristics. Eight urban blocks across the city of Nanjing, China, are selected as case examples. The results show that access structure is capable of accurately describing and evaluating complex spatial relationships between streets, plots and buildings. Access structure is potentially a useful method for studying the complex emerging built form of rapidly changing cities, especially in developing countries such as China.