Sustainability-oriented configurational analysis of the street network of China's superblocks: Beyond Marshall's model

Abstract

The duality in China's traffic planning has given rise to the basic unit of urban form and function called the superblock, which is defined and bound by an arterial street network. The street network of China's superblock underpins the coexistence and interaction of global and local movement, the public and daily space, and affects place diversity and local characteristics. However, its configuration remains to be articulated because of the lack of a systematic representation method, and the associations between configuration and performance, cognition and design cannot be determined. This study proposes an improved representation method for the street network of China's superblocks based on Marshall's route structure analysis to explore the configurational characteristics and sustainability of the network. To fit local conditions, this study improves Marshall's route structure analysis from four perspectives, namely, the judgement of relative hierarchy, the node construction principle, and the deletion and addition of the original indicators. The improved method is then applied to calculate and compare the depth, connectivity, and complexity of the street networks of 10 sample superblocks in Nanjing, which are classified into six types by construction backgrounds, each having two scenarios differing by the level of publicity. Results indicate that the types formed in accordance with the “The Capital Plan” of the Republic of China, which presents a combination of fine orthogonal grids and radiations, and by the renewal of the traditional street-and-lane network, which has the “characteristic structure” defined by Marshall, perform best in terms of configurational sustainability. The analysis also reveals that the addition of semipublic streets formed mainly from the bottom up narrows the sustainability gap among the samples. This study provides a tool for elaborate urban study and design and provides insights into the cognitive and practical aspects of China's urban planning and design.