How does the 3D Built Environment Shape Population Service Coverage in Community Living Circles?A Multi-scale Analysis based on Machine Learning in Xiamen,China
CAI Xingfei
WEN Chaoxiang
WANG Hao
Abstract：As urbanization shifts toward higher-quality development,planning for people-centered community living circles has emerged as an essential strategy for coping with the challenges of traditional expansion and improving the quality of daily life.However,existing studies of such planning methods have two major limitations.First,most studies focus narrowly on the density of public service facilities,overlooking the joint influence of urban spatial form and streets'environmental quality.Second,conventional analytical algorithms often rely on linear assumptions that fail to capture the complicated nonlinear relationship between the built environment and the service capacity of community living circles,as well as threshold effects.In this study,a model involving three-dimensional built environmental indicators of"density-form-quality"was established by using multi-source data from Xiamen,China,including mobile phone signaling,POIs,three-dimensional building,and Baidu street views.The model aims to comprehensively capture,the spatial structure and service functions of community living circles.
To explore how nonlinear effects of the built environment influence efforts to serve populations of living circles,while also capturing threshold effects,the marginal contributions of indicators related to serving such populations were analyzed by using the gradient boosting decision tree(GBDT)algorithm and the SHAP interpretation framework.The model optimization results show good prediction performances of living circles across different scales,indicating that the GBDT-SHAP framework can effectively depict the relationship between built environments and serving populations.Research results reveal two significant features in the mechanisms by which 3D built environments affect efforts to serve populations of living circles:namely,scale differentiation patterns and the nonlinear effect of dominant elements.With respect to scale differentiation,short-scale(5-minute)living circles show multidimensional collaborative features.Serving populations of short-scale living circles is affected not only by spatial form and facility density but also by the spatial quality of streets.Middle-scale and long-scale(10-minute and 15-minute)living circles are mainly influenced by spatial form and the layout of public service facilities.With respect to nonlinear mechanisms,most elements on different dimensions show obvious threshold effects.For spatial form,high-density building environments will weaken the service capacity of living circles after exceeding a specific threshold.Appropriate differences in building height can have a positive regulating effect and relieve the negative impact of high-density development to some extent.For facility density,there are significant differences among dominant types:government-led facilities(e.g.medical service and public transportation)show significant threshold effects,whereas the positive effect of market-led facilities(e.g.shopping)increases continuously with the increase of density,showing insignificant threshold features.This pattern reflects the high level of market adaptation and flexibility of market-led facilities.
This study confirms the scale-dependent and nonlinear effects of 3D built environments on serving populations of living circles,providing a new perspective on the complex mechanisms involved.The study's conclusions have practical value for attempts to optimize differentiated living-circle planning and refined governance.Specifically,an optimized framework with"density-form-quality"synergism should be established.The synergism emphasizes accessibility and livability through reasonable allocation of public service facilities,regulation of building density and height,and improved street environmental quality.Second,planners should apply hierarchical strategy rather than the"one-size-fits-all"planning model.Thus,in 5-minute living circles,key attention should be paid to improve the micro-level spatial quality and walking experience to meet high-frequency and immediate daily needs of residents.In 15-minute living circles,urban spatial structure should be strengthened,through core facility layout and traffic connection,to guarantee the accessibility of large-scale functional activities.Finally,planners should establish a government-market dual-driven optimization pathway to balance the layout and gradient allocation of government-led and market-led facilities.This pathway will afford high-efficiency matching of resource supplies and improve the overall service capacity of living circles.In addition,the proposed method and results lay foundations for comparative studies across cities,which can be undertaken by integrating more demographic data and introducing multiple types of facilities,such as culture,sports,and eldercare services.This approach is conducive to improving the scientific rigor and generalizability of community living circles planning,and can help optimize urban spatial governance.
Keywords：community living circle3D built environmentserving populationsnonlinear relationshipGBDT-SHAPmulti-time scales
Publication Date：2025-12-30
Online Publishing Date：2026-01-08(First online date of this platform, not the publication date of the document)
Pages：9( 34-42 )