Dense Urban Context Research Articles

The importance of private gardens and their spatial composition and configuration to urban heat island mitigation

Small Urban Green Infrastructure (UGI; green areas < 2 ha) represents the best opportunity to mitigate Urban Heat Island (UHI) and directly promote microclimate regulation. However, few studies investigate the cooling capacity (CC) of small UGI and how their spatial organization influences its provision. Here, we used an urban cooling model and landscape metrics to understand how UGI in public and private domains influences microclimate regulation in a dense urban region of Rio de Janeiro. Our findings highlight the significant correlation between private UGI and CC, explaining over 80 % of its variation. We found an interaction between UGI composition (i.e. the amount of UGI) and configuration (i.e. spatial distribution of UGI). Nevertheless, UGI configuration exerted the greatest influence with edge density being the most significant landscape metric, suggesting that, with an equivalent green area, patchwork or numerous smaller green areas enhance CC compared to fewer larger ones. This study underscores the pivotal role of private UGI organization in tropical and dense urban context, where public UGI is neglected. We conclude that UGI awareness initiatives must systematically pay attention to spatial configuration of the small UGI, aligning interventions with urban dwellers' needs in order to guarantee microclimate regulation provision.

Influencing factors of spatial vitality in underground space around railway stations: A case study in Shanghai

Developing urban underground space for transportation and commercial purposes has become a vital strategy for sustainable urban growth, especially in dense urban contexts. The vitality of underground space has received wide attention as a key indicator of its efficiency and performance. The spatial vitality of underground space is affected by many factors, including function, spatial configuration, transport environment, and pedestrian-oriented design features. This study takes the underground space of Shanghai Hongqiao Business District (Phase I), one of the most successful integrated railway station-city development projects, as a case to explore the spatial and temporal distribution characteristics of spatial vitality and its influencing factors. Multilevel linear models were used to analyze the relationship between pedestrian flow and its influencing factors. Random forest models were used to investigate the relative importance of influencing factors on spatial vitality. This study verified that the distance to the transportation hub and spatial configurations calculated by space syntax are the two most essential factors for vitality. The number of retail stores and walkway width impact the vitality on weekends. The results shed light on our understanding of the urban vitality in the underground space and provide some tentative suggestions for the planning and design of underground space in high-density cities.

The nonlinear relationship between the active travel behavior of older adults and built environments: A comparison between an inner-city area and a suburban area

The nonlinear relationship between the built environment and active travel among older adults within the inner-city context has been widely researched. However, limited attempts have been made to explore the demographic and spatial heterogeneity of the built environment's effects in dense urban or peripheral urban contexts. With the outward urban expansion brought about by rapid suburban growth in Chinese cities, there have been dynamic built environment, service, and socioeconomic composition changes in the suburbs. Using data from Xiamen, China, this study employs a BO-LightGBM method to fill this gap among different cohorts of the aging population (different personal statuses and family relationships) within two contexts, and the SHAP method is adopted to interpret the models with distinctive spatial patterns of built environment differentiation. Our results show that differentiation in the threshold values and gradients exists between built environment associations and the elderly's active travel in Inner Xiamen and Outer Xiamen. The contribution of built environment variables to impact older adult's active travel is related to the regional context as well as demographic characteristics. These results offer nuanced and contextualized built environment interventions for building age-friendly cities.

A novel and efficient method for calculating beam shadows on exterior surfaces of buildings in dense urban contexts

To address the challenges associated with the efficiency of calculating beam shadows on building exterior surfaces in dense urban contexts being low, a novel “neighbourhood shading building surfaces” determination criterion is proposed. The criterion was applied to the beam shadow calculation methods to evaluate its effectiveness in two case studies, one fictitious and simplified and the other real and complex. The results show that the novel criterion can efficiently and precisely determine the neighbourhood building surfaces that may shade the target buildings compared with the existing one. In addition, the efficiency of calculating beam shadows on building exterior surfaces in dense urban contexts is significantly enhanced after applying the novel determination criterion. Compared with the shadow calculation methods without neighbourhood judgement, the calculation accuracy is similar, while the total shadow calculation time is reduced by approximately 92% when the proposed criterion is integrated. Compared with the shadow calculation methods using the existing neighbourhood judgement criterion, both the calculation accuracy and efficiency are improved when the proposed criterion is integrated, showing a 68% reduction in the total shadow calculation time. It is also demonstrated that the analytical method (i.e., the polygon clipping method) integrated with the new criterion is more efficient and accurate for calculating beam shadows on exterior surfaces of buildings in dense urban contexts.

ZERO-ACREAGE FARMING DRIVING SUSTAINABLE URBAN DEVELOPMENT: A SPATIAL AND TECHNOLOGICAL COMPARISON OF URBAN AGRICULTURE FARMS

ABSTRACT Zero-Acreage Farming (ZAF) recently developed as a novel land-use form and is aimed at addressing food security and sustainable urban development. While it is often lauded as a sustainable land-use form with potential to improve resource consumption and urban sustainability, little research into the spatial and technological requirements of this land-use form is available. This study undertakes a comparative analysis of ZAF and ground-based urban agriculture (UA) farms in diverse countries to differentiate their technical and spatial implementation parameters and uncover ZAF-specific characteristics and their implementation feasibility in rapidly developing cities. This qualitative study uses semi-structured interviews, triangulated with observational studies, to document ZAF and UA farms in South Africa, Belgium, the Netherlands and Singapore. The findings reveal UA as highly flexible, modular landuse forms while, contrastingly, the technological focus of ZAF farms often results in monofunctional and inflexible once implemented, isolated, and non-contextual solutions. While ZAF farms are appropriate to improve livelihoods and food security in dense urban contexts, the study highlights trends that must be addressed to promote the implementation of ZAF in poorer rapidly developing cities.

Livable neighborhoods for sustainable cities: Insights from Barcelona

The paper proposes a reflection on the superblock model - or supermanzana, in its well-known Spanish application - in the context of the debate on the 15-minute city and on the functional reorganization of mobility and public space to improve the quality of life, health and accessibility in urban areas.The impacts of car traffic on the livability of cities and neighborhoods, in terms of safety, air pollution, noise, but also in terms of consumption and quality of public space, are widely acknowledged. These issues are not new to the debate: since the first decades of the 20th century, with the advent and rapid diffusion of the automobile, concerns on the impacts of vehicular traffic and issues of urban livability and traffic separation have been raised by urban and transport planners. As a consequence, various models of neighborhood planning emerged, proposing solutions to limit these impacts.The supermanzana model takes up the principles of neighborhood planning by identifying a main road network and setting up a system of superblocks within the meshes of this network, in order to improve accessibility, equity, health and livability; it aims on the one hand to transform public spaces at the neighborhood level and on the other hand to reorganize the existing urban structure. The application of the supermanzana model in Barcelona offers an interesting contribution to the debate on the 15-minute city, showing how the principle of traffic separation can be applied to existing, dense urban contexts, reclaiming public space to more livable neighborhoods and sustainable cities. The analysis of the case study of Barcelona can contribute to research and policy, learning from this experience and especially from the critical issues that emerged.

An End-to-End Point of Interest (POI) Conflation Framework

Point of interest (POI) data serves as a valuable source of semantic information for places of interest and has many geospatial applications in real estate, transportation, and urban planning. With the availability of different data sources, POI conflation serves as a valuable technique for enriching data quality and coverage by merging the POI data from multiple sources. This study proposes a novel end-to-end POI conflation framework consisting of six steps, starting with data procurement, schema standardisation, taxonomy mapping, POI matching, POI unification, and data verification. The feasibility of the proposed framework was demonstrated in a case study conducted in the eastern region of Singapore, where the POI data from five data sources was conflated to form a unified POI dataset. Based on the evaluation conducted, the resulting unified dataset was found to be more comprehensive and complete than any of the five POI data sources alone. Furthermore, the proposed approach for identifying POI matches between different data sources outperformed all baseline approaches with a matching accuracy of 97.6% with an average run time below 3 min when matching over 12,000 POIs to result in 8699 unique POIs, thereby demonstrating the framework’s scalability for large scale implementation in dense urban contexts.

Natural ventilation for office building retrofit in dense urban context under hot and humid climate

Abstract Recent studies underline that simple and non-invasive retrofit solutions can recover natural ventilation potential in existing buildings under temperate climate. Nonetheless, the efficiency of these solutions in dense urban contexts under hot and humid climate remains unclear. This paper aims to evaluate the thermal comfort gains caused by natural ventilation when retrofitting an office building in downtown Rio de Janeiro. Computational Fluid Dynamics (CFD) and thermal simulations are carried out on Ansys CFX and Design builder to assess indoor air flow before and after retrofit. The diagnosis of the current scenario indicates that the surrounding buildings block a significant part of the wind flow, and occupants experience only a few hours of thermal comfort during the year, especially on lower floors. To increase indoor air flow, the fixed upper windows were transformed into pivot windows and kept open permanently. This measure increases the annual hours of thermal comfort by 0.5-35%, depending on the floor and the adaptive comfort model. These findings suggest that natural ventilation itself may not be sufficient to ensure occupants' comfort throughout the year under the investigated context.

A New Approach to Assess the Built Environment Risk under the Conjunct Effect of Critical Slow Onset Disasters: A Case Study in Milan, Italy

Citizens in dense built environments are susceptible to the simultaneous occurrence of Slow Onset Disaster (SLOD) events, being particularly prone to increasing temperatures and air pollution. Previous research works have assessed these events’ arousal separately and have identified when their intensity is critical. However, few have integrated their analysis, possibly limited by the quality and granularity of available data, the accessibility and distribution of sensors, and measurements not emulating the surroundings of a pedestrian. Thus, this work performed an outdoor meso-scale multi-hazard-based risk analysis to study the aggregated effects of the SLODs mentioned above. The study was carried out to narrow down the time-frames within 2019 in which these two events could have affected citizens’ health the most. A weighted fuzzy logic was applied to superimpose climatic (temperature, humidity, wind speed, and solar irradiance) and air quality (particulate matter, ozone, and ammonium) distress (true risk) on an hourly basis, allocated using set healthy and comfortable ranges for a specific dense urban climate context within Milan (Italy), processing data from Milano via Juvara station. The findings show that sensitive groups were at risk of high temperature and pollution separately during 26% and 29% of summer and mid-season hours, respectively; while multi-hazard risk would arise during 10.93% of summer and mid-season hours, concentrated mainly between 14:00 and 20:00.

Planning of Urban Green Spaces: An Ecological Perspective on Human Benefits

In the context of urban land-use growth and the consequent impacts on the environment, green spaces provide ecosystem services for human health. The ecosystem services concept synthesises human–environmental interactions through a series of combined components of biodiversity and abiotic elements, linking ecological processes and functions. The concept of green infrastructure (GI) in the urban context emphasises the quality and quantity of urban and peri-urban green spaces and natural areas. In dense urban contexts, the applications of GI are limited and not applied to the potential urban spaces such as roofs and gardens. Often, roofs are characterised by impermeable paved surfaces with negative effects on human well-being, whereas garden designs do not consider social needs and environmental interactions. The role of urban stressors or the urban context as a driving force or pressure of urban green space is not always well understood and employed in the planning of green spaces. This is partly due to a knowledge gap between different science disciplines that operate on different scales, from single processes of the plants (which focus on plant responses to environmental stresses affecting human well-being) to urban ecosystems (which focus on the biodiversity and urban space planning–human well-being relationship). This can create a paradox, as green spaces that are not adequately designed might not produce the expected effects. In this paper, an overview of benefits and limitations of applying the ecosystem services approach when designing green spaces is presented. The focus is on the main urban ecosystem services provided by green roofs and community gardens such as GI that can represent strategies to provide ecological and social multifunctionality to waterproofed surfaces connected to the buildings and low-exploited gardens being the main areas that affect dense urban settlements, and thus, increasing the ecosystem services in the urban environment, such as reducing the Urban Heat Island, as well as flooding events. Specifically, the paper highlights (i) feedback between ecological processes and functions that support ecosystem services, (ii) urban environmental stresses in relation to disservices that these can create for human well-being and (iii) key issues that should be considered in the planning and design of urban ecosystem services. Such a new vision of urban ecosystem services highlights the need to look at GI as an active part of the urban space design in the built environment.

Effect of surface treatment and built form on thermal profile of open spaces: A case of Mumbai, India

The thermal environment in Recreational Open Spaces (ROS) is primarily a result of the surrounding built form which includes buildings, trees, and surface treatment materials. To study the impact of land surface treatment choice and urban form on the thermal characteristics of open spaces, a case study assessment was undertaken in the dense urban context of Mumbai, India. To study ROS and its thermal profile, we selected three open spaces adjoining a school in Mumbai exhibiting different surface material treatments and built form. A comparative analysis was done using ENVI-met model. The model outcomes were validated using field measurements. The results highlighted the significant impact of the land surface choice and vegetation on the ambient air temperature and surface temperature of ROS. Open spaces with concrete paving and open mud surface showed the air temperature about 3 °C and 1.5 °C higher than the surfaces covered with tree litter. During the evening, concrete surfaces showed that maximum surface temperature (Ts) was comparatively higher (4 °C), as compared to others. The inferences from this study would assist in appropriate policy formation and design guidelines that could favourably impact the thermal profile of ROS and aid in mitigating the urban heat island effect.

The influence of building form variables on the environmental performance of semi-outdoor spaces. A study in mid-rise and high-rise buildings of Singapore

This study delved on the role of semi-outdoor spaces (SOS), as form-based strategies, in providing enhanced, thermally comfortable environments in highly dense urban contexts. A sample of sixty-three (63) SOS was studied, within four different mid-rise and high-rise buildings located in the warm-humid tropical city of Singapore. It was found: (i) that SOS may act as thermal buffer spaces; (ii) that microclimate creation in SOS is linked to form, specifically to geometrical variables such as void-to-solid ratio, height, height-to-depth ratio, height from ground level, green plot ratio and open space ratio, which influence significantly the environmental factors of air temperature, mean radiant temperature, air velocity and relative humidity; (iii) that some aforementioned geometrical variables (height-to-depth ratio and open space ratio) are linked to thermal comfort when estimated with SET* and PMV* thermal indices; (iv) and that thermal comfort (between −1 and +1 PMV*) can be achieved in SOS considering a typical Singaporean outdoor CLO of 0.3, especially for 1 MET (85.7% of SOS). In the context of Singapore, this study demonstrates that incorporating SOS to mid-rise and high-rise building forms promotes the creation of thermally comfortable microclimates suitable for human activity, even during the hottest hours.

Built environment, commuting behaviour and job accessibility in a rail-based dense urban context

This study examines how job accessibility, as measured in commute distance and commute duration, is associated with different built environment features in a rail-based high-density urban context--Hong Kong. As a major contribution of this research, our analyses demonstrate that the average effects of built environment features on people’s commuting patterns and job accessibility mask considerable heterogeneity across different commute modes and neighborhood types. Using multiple regression models, we found that public transit commuters are more responsive to changes in built environments than private vehicle commuters. Subdivided samples also show that several built environment features affect job accessibility in job-dense downtown neighborhoods differently than in other types of neighborhoods (i.e. non-downtown urban neighborhoods, new town neighborhoods, rural neighborhoods), suggesting the nonlinearity in these relationships. This research has important implications to urban policymaking, especially in addressing the needs of different transit users (rail, bus, mixed) versus automobile users, as well as the needs of different types of neighborhoods. The findings and policy recommendations can reasonably be generalized to other major cities with similarly dense settings.

The association between spatial access to physical activity facilities within home and workplace neighborhoods and time spent on physical activities: evidence from Guangzhou, China

BackgroundUrban residents from the developing world have increasingly adopted a sedentary lifestyle and spend less time on physical activities (PA). Previous studies on the association between PA facilities and individuals’ PA levels are based on the assumption that individuals have opportunities to use PA facilities within neighborhoods all day long, ignoring the fact that their willingness and opportunities to use nearby facilities depend on how much discretionary time (any time when people have a choice what to do) they have. Further, scant attention has been paid to the influence of PA facilities within both residential and workplace neighborhoods in the dense urban context. To address the above research gaps, this study investigated the links between the spatial access to PA facilities within home/workplace neighborhoods and time spent on PA among working adults, focusing on whether results were different when different measures of accessibility were used and whether participants’ discretionary time over a week affected their time spent on PA.MethodThis study used data from a questionnaire survey (n = 1002) in Guangzhou between June and July 2017 and point of interest (POI) data from online mapping resources. Outcome variables included the amount of time spent on physical activity/moderate and vigorous intensity physical activity (PA/MVPA) over the past week. Home/workplace neighborhoods were measured as different distance buffers (500 m circular buffers, 1000 m circular buffers, and 1080 m network buffers) around each respondent’s home/workplace. Spatial access to PA facilities was measured using two indicators: the counts of PA facilities and proximity to PA facilities within home/workplace neighborhoods. The amount of discretionary time was calculated based on activity log data of working day/weekend day from the Guangzhou questionnaire survey, and regression models were used to examine relationships between the spatial access of PA facilities, the time spent on PA/MVPA, and the amount of discretionary time, adjusted for covariates. Associations were stratified by gender, age, education, and income.ResultsUsing different measures of accessibility (the counts of and proximity to PA facilities) generated different results. Specifically, participants spent more time on PA/MVPA when they lived in neighborhoods with more PA facilities and spent more time on MVPA when worked in closer proximity to PA facilities. A larger amount of discretionary time was associated with more time spent on PA/MVPA, but it did not strengthen the relationship between access to PA facilities and PA/MVPA time. In addition, relationships between access to PA facilities and PA levels varied by gender, age, education, and income.ConclusionThis study contributes to the knowledge of PA-promoting environments by considering both the home and workplace contexts and by taking into account the temporal attributes of contextual influences. Policymakers and urban planners are advised to take into account the workplace context and the temporal variability of neighborhood influences when allocating public PA facilities and public spaces.

Thermal behaviour of concrete and corrugated zinc green roofs on low-rise housing in the humid tropics

This study focused on two types of roof spaces: concrete and corrugated zinc. Both green roofs were covered with short-lived productive vegetables throughout dry and rainy seasons, monitored by an infrared thermometer and a wet-bulb-globe thermometer. The results show that the green roofs in the humid tropics had significant thermal insulation capabilities, with a decline in thermal conductivity, of up to 57.1% from 1.99 to 0.85 W/(m K) in the concrete roofs, and 90% from 5.87 to 0.59 W(m K) in the corrugated zinc roofs. As opposed to non-green roofs, green roofs could reduce heat flow by up to 56% from 19.3 to 8.5 W/m2 in concrete and could reach 50.8% from 39.6 to 19.5 W/m2 in corrugated zinc. Green roofs over humid tropical dwellings are therefore useful for improving environmental microclimates, particularly in dense urban contexts.

An Examination of Last Mile Delivery Practices of Freight Carriers Servicing Business Receivers in Inner-City Areas

Freight carriers experience major challenges while operating in highly dense inner-city areas. Timely deliveries are crucial for the success of businesses and for the long-term economic growth of metropolitan areas. Previous freight studies have paid little attention to the characteristics of freight movements in a highly dense urban context. Accordingly, this study sought to quantify the operational practices for freight carriers that deliver light parcels to inner-city business receivers. Direct insights were collected using semistructured interviews and an online survey with freight carriers in Melbourne, Australia. The intent was to describe the delivery trips and vehicle types involved in this unique segment. An assessment of operational challenges to the efficiency of freight carriers is presented in the study. In general, freight deliveries to inner-city receivers are characterised by underutilised transport capacity along with a large number of delivery stops. The findings shed light on the challenges that couriers encounter in congested inner-city areas.

Towards the Valuation of Open Spaces: A Hedonic Based Investigation for Sustainable Planning in the Dense Urban Context of Dhaka

Within the context of the economic valuation, the presence and absence of open space has an effect on the residential property value in urban areas. Residents in a city esteemed these open spaces differently. They are keen to pay a premium for attractive views willingly. This study only assessed the amenity value of open spaces especially green parks and water bodies of two planned urban residential neighborhoods of Dhaka city in Economic terms. An empirical analysis is carried out by employing Hedonic Price Method (HPM) to analyze the impact of open space attributes on real price of residential properties. The six storied walkup and high-density apartments are typical for upper and middle-income residents in Dhaka city. Together with a set of structural, location and socio-economic variables the research use to explain residential property prices; this study focuses on three amenity or environmental variables which include the existence of views of open spaces, the distance from the residential unit to the nearest open space, and the size of that open space. The regression analysis result from the first stage hedonic estimation reveal that homebuyers are willing to pay only for scenic views and living in the closest proximity to open spaces especially green parks. In contrast results for the size of the nearest open space for houses do not show a significant relationship on nearby property values. This estimated valuation of open spaces and their amenity benefits will be useful for policy making in urban design for both developers and planners, composing new strategies for land use planning and sustainable development, open space conservation and property appraisal.

Inter-building assessment of urban heat island mitigation strategies: Field tests and numerical modelling in a simplified-geometry experimental set-up

Large scale mitigation strategies showed to represent promising solutions for enhancing liveability in dense urban contexts. Therefore, most of the researches are focused on assessing the effect of high albedo surfaces and greenery. The paper deals with a numerical and experimental analysis of these evapotranspiration and high-reflectance surfaces in a full scale experimental set-up where more than 20 cubicles are monitored in a Mediterranean continental climate. The experimental set-up itself covers an intermediate inter-building perspective between the lab scale and the real urban contexts, which compromises the possibility to generalize final results. This scale is able to better control geometry of area, but allows real microclimate monitoring and calibration of CFD models. Starting from a validated model, this study simulated alternative scenarios with gradually varying the presence of common mitigation strategies with the scope to evaluate their effect to this aim. Results showed that high albedo solutions best mitigate summer overheating reducing the air temperature, while greenery was more effective in the densest configurations with low albedo envelopes, showing how geometry related variables may play a key role in determining the optima configurations of microclimate mitigation strategies, also important for the best exploitation of renewables in the built environment.

Neighborhood Experiences of People Over Age 50: Factor Structure and Validity of a Scale.

Various aspects of the neighborhood environment have been shown to correlate with older adults' health. Socio-ecological models of health posit that interventions in the living environment can influence population health. Yet, there are no scales to comprehensively measure older people's experiences of their neighborhoods especially in dense urban contexts. This study analyzes the psychometric properties and factor structure of a holistic measure of Older People's Neighborhood Experience (OpenX) to understand constituent factors of residential satisfaction and well-being in dense urban contexts. Participants were 1,011 community-dwelling older adults aged 50 and older in Singapore. Face-to-face interviews were conducted. Questions were drawn to measure physical and social aspects of the neighborhood as well as sociodemographic variables. Exploratory and confirmatory factor analyses were conducted to obtain a shorter version; content validity, internal consistency, and external validity were assessed. The OpenX has a 4-dimensional structure, explaining 45.5% of the variance of neighborhood experience. They are communal affordance, embeddedness, environment pleasantness, and time outdoors. Good reliability and validity were found, including Cronbach's alpha of 0.827. The correlation between neighborhood experience and objectively measured proximity to parks and fitness corners approached significance (p = .082). The 16-item OpenX demonstrated good psychometric properties. With reference to the transdisciplinary neighborhood health framework, it is useful for assessing older adults' neighborhood environment, identifying neighborhoods for pilot population health interventions, and understanding how the neighborhood environment affects older adults' health.

Solving Traffic Congestion through Street Renaissance: A Perspective from Dense Asian Cities

Traffic congestion is one of the most vexing city problems and involves numerous factors which cannot be addressed without a holistic approach. Congestion cannot be narrowly tackled at the cost of a city’s quality of life. Focusing on transport and land use planning, this paper examines transport policies and practices on both the supply and demand sides and finds that indirect travel demand management might be the most desirable solution to this chronic traffic ailment. The concept of absorption of traffic demand through the renaissance of streets as a way for traffic relief is introduced from two perspectives, with some examples from dense Asian urban contexts to demonstrate this. Firstly, jobs–housing balance suggests the return of production activities to residential areas and sufficient provision of diverse space/housing options to deal with work-related traffic. The second approach is to promote the street as a multi-activity destination rather than a thoroughfare to access dispersed daily needs, and to advocate more street life to diminish non-commuting traffic. Based on this, suggestions for better transport planning policies are put forward.