Abstract
Urban vibrancy can facilitate human activities and social interactions, attract capital and talent, enhance competitiveness and creativity, maintain resilience, and finally achieve a sustainable urban development. Theoretically, transit-oriented development (TOD) is beneficial for urban vibrancy. In practice, TOD implementation does not always lead to vibrant community life. Understanding relationships between TOD-ness (i.e., the degree to which the current physical conditions of station areas meet the standards of TOD) and urban vibrancy is crucial to foster vibrancy around stations.Empirical studies on this topic are scarce, despite numerous studies on the effects of built environment/urban morphology/urban landscape on vibrancy. These previous studies are likely to overestimate or underestimate the effects as most of them neglect the pervasive nonlinearity and synergism. Moreover, geographic contexts are seldom considered. As places are interconnected with one another, one place’s vibrancy depends on not only that place’s attributes but also those of other places related to it. Incorporating geographic contexts can help better examine the effects. This research contributes to the understanding of TOD effects on urban vibrancy from the perspectives of nonlinearity, synergism, and geographic context.
This research avails of multi-source geo-tagged big and/or open data from 166 metro station areas (MSAs) in Shenzhen, China to develop index/indicators for measuring urban vibrancy and TOD-ness. Vibrancy is measured by a composite index integrating multiple proxies: metro ridership, population density, social activity intensity, and economic activity intensity. TOD-ness is delineated from three dimensions based on the “node–functionality–place” model, namely, transport (node), walking environment (functionality), and land development (place).
Employing gradient boosting decision tree (GBDT) and Shapley additive explanations (SHAP), this study locally reveals the relative contributions, nonlinear effects, and synergistic effects of/among TOD-ness indicators on urban vibrancy in Shenzhen, China. This research finds the following: (1) Sufficient bus services, horizontal built-up coverage, and mixed-use buildings are dominant contributors to vibrancy around metro stations. (2) TOD-ness indicators have pervasive nonlinear influences on urban vibrancy. (3) Synergistic effects are evident among/within TOD-ness indicators/dimensions.
Furthermore, this study designs four scenarios (i.e., null, distance, network topology, and spatial interaction) to reflect geographic contexts of MSAs and encodes them into graph convolutional neural network (GCNN) models. Several two-layer GCNN models are built with geographic contexts considered, TOD-ness indicators as input, and vibrancy indicators/index as output. By comparing the model performance, this research finds that (1) incorporating geographic contexts can promote the prediction power of the GCNN models and thus can help better examine the vibrancy effects of TOD, (2) the spatial interaction metric can better reflect geographic contexts than the other metrics can, and (3) the composite vibrancy can be well predicted.
Finally, based on the understanding of nonlinear and synergistic effects of/among TOD-ness variables on urban vibrancy, practical implications, such as targeted policies with nuanced planning/design criteria, are further discussed. This research also utilizes residuals of the GCNN model to reflect on the efficacy of TOD in cultivating urban vibrancy and highlights the importance of placing station areas within their specific geographic contexts.
This study enriches the understanding of nonlinear and synergistic effects of TOD on urban vibrancy as well as the role of geographic contexts. The findings can provide insights for tailoring nuanced planning/design criteria for promoting vibrancy in station areas.
| Date of Award | 8 Jul 2021 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Siu Ming LO (Supervisor) |