Exploring Traffic Planning Networks across Multiple Scales Based on Urban Morphology: A Case Study of Nanjing, China

The traffic planning network (TPN) represents future urban development and holds particular significance for the growth of cities. Although urban morphology (UM) has been applied to traffic networks, there exists a lack of multiscale quantitative research on TPN. From the UM perspective, this paper develops a quantitative framework to achieve the extraction and analysis of multimorphological features of TPNs on spatiotemporal scales. Subsequently, we investigated the morphological evolution of TPNs in Nanjing, China, from the 1980s to the 2020s. The research reveals the following findings: (1) In terms of spatiotemporal scales, the Nanjing TPN exhibits a multicentric agglomeration pattern on a smaller scale, evolving from discrete points to urban belts; on a larger scale, the urban framework transitions from a cross-shaped axis to a circular radial form. The evolution of Nanjing's form zones shows a southward shift of the Core zone and a transition from agglomeration to expansion and then gradual stabilization in the periphery of the Core zone. (2) The quantitative framework we proposed effectively extracts morphological characteristics within TPNs, visualizing the focal points and trends in urban traffic planning. (3) These morphological characteristics create Nanjing's heart-shaped layout, also reflecting the evolution of planning concepts from concentric urban groups to urban–rural integration. Our study enriches research on traffic planning and UM and offers valuable insights for traffic planning in Chinese cities.