Urban Planning Strategies Research Articles

Investigating the Effect of Transit-Oriented Development (TOD) on Social Equity—Examining the Displacement of Footscray, Melbourne

As Melbourne faces exponential population growth, the necessity for resilient urban planning strategies becomes critical. These strategies include mixed land use, density, diversity, and sustainable transportation through transit-oriented development (TOD). While TOD promises to accommodate growing populations and address environmental concerns, it also raises issues regarding its unintended consequences on poverty and inequality, notably through residential displacement and gentrification. This study investigates the impacts of TOD construction on inequality in Footscray, employing spatial analysis techniques like the hedonic price model (HPM), robust regression analysis, and Pearson correlation analysis. It aims to understand how spatial factors influence housing prices and their correlations. Additionally, the study uses observational spatial analysis via Google Street View (GSV) to examine indices such as housing development type, traffic signage, sanitation facilities, and house beautification. This approach seeks to build an evaluation framework to assess the extent of TOD street reconstruction and its impact on gentrification and displacement. The research adapts existing knowledge to create a tool for reviewing past planning decisions and assessing the fairness of TOD planning implementation. By providing assessment and guidance to mitigate the potential adverse impacts of TOD, this study contributes to the advancement of urban-planning practices, offering insights into mixed land use and effective strategies to balance economic development and social equity, thereby enhancing community resilience. Ultimately, this research deepens our understanding of the impacts of TOD on urban inequality and offers practical tools and insights for more equitable and sustainable urban development.

Living on the edge: nature preserves as an oasis for birds, bats, and other mammals in the urban desert and concrete jungle

Increasing urbanization threatens a variety of vital vertebrate habitats, including those of birds, and both terrestrial and aerial mammals. Nature preserves near urban centers at the rural/urban interface may harbor natural areas which can help to offset loss of habitat as cities expand. Therefore, techniques which allow managers to conduct short term surveys for vertebrates are needed. I conducted non-invasive, passive camera trapping and acoustic surveys in the vicinity of the urban area of Charlotte, North Carolina across 8 sites within Mecklenburg, Cabarrus, and Union counties during summer to fall 2023 to collect data on avian and mammalian communities. Five species of bats were documented, alongside 39 birds, and 11 terrestrial mammals. Bat activity decreased consistently along the sample period whereas terrestrial mammals were consistently sampled during the same time frame, with early summer providing effective data on avian presence. Automated identification software followed by manually vetting for bats and birds was effective in documenting diversity alongside camera trapping. The results presented here provide baseline data for future monitoring to inform urban planning management strategies and future studies on the potential presence of avian and mammalian presence in nature preserves.

In the Spotlight: Bat Activity Shifts in Response to Intense Lighting of a Large Railway Construction Site

Artificial light at night (ALAN) is a major form of anthropogenic pollution, disrupting nocturnal wildlife behaviour and ecosystem function. Large construction sites are typically located at the intersection of urban and natural areas, introducing intense lighting into previously dark natural habitats. This study examines the responses of bats to intense nighttime lighting at a major construction site associated with a linear transport infrastructure (LTI) project. We used passive acoustic monitoring to record bat activity and species richness at the construction site and in adjacent urban and natural areas with different lighting levels. Generalist species, such as Pipistrellus kuhlii and Nyctalus leisleri, were attracted to illuminated areas, likely due to increased prey availability. Conversely, sensitive species, such as those from the Myotis and Plecotus genera, along with Barbastella barbastellus, avoided illuminated areas, particularly the construction site. Species richness was significantly lower at the construction site compared to other environments, reflecting ALAN’s barrier effect on movements and habitat accessibility for more sensitive species. The findings highlight the ecological impacts of introducing ALAN to previously unlit natural environments, underscoring the urgent need for implementing ALAN mitigation strategies in urban planning and construction practices to protect biodiversity in urbanising areas.

Investigating neighborhood adaptability using mobility networks: a case study of the COVID-19 pandemic

What predicts a neighborhood’s adaptability to essential public health policies and shelter-in-place regulations that prevent the harmful spread of COVID-19? To answer this question, we present a novel application of human mobility patterns and human behavior in a network setting. We analyze 2 years of mobility data (January 2019 to December 2020) from New York City and construct weekly mobility networks between census block groups based on aggregated point-of-interest visit patterns. Our results indicate that neighborhoods’ socioeconomic and geographic characteristics play a significant role in predicting their adaptability to active shelter-in-place policies. Our simulation outcomes reveal that, alongside factors such as race, education, and income, the geographical attributes of neighborhoods, such as access to amenities that satisfy community needs are equally important factors in predicting neighborhood adaptability to public health policies. These findings offer valuable insights that can enhance urban planning strategies, thereby aiding pandemic mitigation efforts and fostering increased adaptability of urban areas in the face of exogenous shocks like the COVID-19 pandemic.

Revisiting the relationships between energy consumption, economic development and urban size: A global perspective using remote sensing data

Existing methods of measuring energy consumption require complex statistics and computing. A real-time and globally applicable approach for comparing energy consumption across different cities is still lacking. Additionally, the nonlinear relationships and varying thresholds of energy consumption in relation to economic activities and urbanization remain unconfirmed. This study aims to fill these gaps by utilizing Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite (NPP-VIIRS) nighttime light data in 2015 and a top-down approach based on a multiple regression model to examine energy consumption in global cities employing a redefined urban boundary. It also explores the accurate relationship between energy consumption, population density (as a proxy of urbanization), and per capita gross domestic product (GDP) across different regions and urban sizes using generalized additive models and regression models. High-resolution gridded population and GDP datasets covering the entire planet are utilized for this purpose. The study also estimates the development potentiality. The study yields followings outcomes: Firstly, the top 30 cities with the highest per capita energy consumption account for over 0.66% of the total per capita energy consumption of all cities. Secondly, in East Asia (EA) and Southeast Asia (SEA), the per capita energy consumption decreases when per capita GDP reaches $40,000 and $75,000, respectively, while it remains stable in cities located in Western Europe (WE) and North America (NA) as per capita GDP increases. Thirdly, the per capita energy consumption declines with increasing urban population density until reaching 10,000 person/km2, 22,000 person/km2, and 4000 person/km2 in EA, SEA, and NA, respectively. Fourthly, in Central Asia (CA), megacities can save over 100 Mbtu/population when per capita GDP increases by $1000 compared to big cities. This pioneering study provides a comparable investigation of energy consumption at the global city level, exploring its relationship with urbanization and economy by employing a unified calculation standard. It will facilitate long-term energy-saving policies and urban planning strategies.

Progress in the Application of Multi-Temporal Remote Sensing Technology in Urban Land Use Monitoring

This study leverages multi-temporal remote sensing technology to analyze urban land use dynamics across various Indian cities over the last decade, providing a nuanced understanding of urban expansion and its implications for sustainable development. Employing high-resolution satellite imagery and advanced image processing techniques, the research captures detailed changes in land use patterns, highlighting the encroachment on agricultural lands and green spaces due to urban sprawl. Through a comprehensive analysis of socio-economic drivers, policy frameworks, and environmental consequences, the study sheds light on the complex interplay between urbanization, socio-economic disparities, and environmental sustainability. It discusses the implications of policies such as the Special Economic Zones (SEZs) Act on land conversion rates and explores mitigation strategies, including green infrastructure, urban agriculture, and sustainable land management practices. The findings advocate for integrated urban planning strategies that balance development with sustainability, offering valuable insights for policymakers, urban planners, and the broader academic community. This research not only advances our understanding of urban land use dynamics in India but also underscores the global relevance of employing remote sensing technology for sustainable urban development.

Safety-centric urban engagement plan

Research objective: The objective of this study is to assess the efficacy of a Safety-Centric Urban Engagement Plan (SCUEP) that intends to improve the safety of city centres by actively involving the community. This study investigates the impact of heightened social engagement in public areas on the safety and overall welfare of individuals residing in urban metropolis centres.
 Methodology: The research adopts a mixed-methods approach, combining quantitative data analysis of crime rates and qualitative assessments of community perceptions before and after the implementation of SCUEP. It also includes case studies from various municipalities that have adopted similar engagement plans.
 Main findings: The results show a direct correlation between heightened social participation and reduced crime rates in city centers. Improved lighting, well-maintained public spaces, and community events correlate with increased public use of city centers and a consequent reduction in crime.
 Application of the study: The findings offer practical insights for urban planners, legislators, and law enforcement authorities. The significance of engaging local populations in safety measures is emphasised, indicating that successful urban involvement can result in enduring safety solutions in city centres.
 Originality/Novelty of the study: The study brings a novel perspective by linking urban design and social engagement with urban safety. It introduces SCUEP as an innovative framework that integrates community-led activities, urban planning, and law enforcement strategies to foster safe and inclusive city centers.

Refocusing on nature: the role of nature reintegration in environmental, mental, and societal wellbeing.

This perspective paper investigates the dynamic interplay between wealth, materialism, environmental degradation, and mental health amid escalating challenges of climate change. The paper critically examines how affluence, often a buffer against climate impacts, paradoxically leads to higher consumption and carbon footprints, exacerbating environmental problems. A societal emphasis on materialism contributes to an estrangement from nature, with significant implications for mental health and environmental sustainability. The paper proposes a fundamental shift in addressing these intertwined challenges through reintegration with nature. The paper recommends integrating urban planning, education, mental health, and community engagement strategies to build a sustainable, mentally resilient society more integrated with nature. This approach, supported by future research directions, aims to create a more balanced, environmentally conscious, and mentally healthy world.

Vertical Green Landscape Facades as a Reducer of Pollution in High Density Cities: A Review

As urbanization continues to intensify, high-density cities grapple with escalating environmental and social challenges that directly impact the well-being of their inhabitants. This paper explores the potential of vertical green landscape facades as a pragmatic solution to mitigate these issues while fostering sustainability within urban environments. In recent times, vertical green landscape design concepts have garnered increasing attention and popularity for their ability to combat pollution and enhance the quality of life in densely populated urban areas. This paper delves into the manifold benefits of vertical green landscapes, as demonstrated by recent research, focusing on their positive reception among the public and their capacity to offer novel avenues for developing green infrastructure. Through an in-depth analysis of relevant literature and case studies, this paper evaluates the role of vertical green landscapes as an effective reducer of pollution in high-density cities. It discusses their capacity to mitigate air and noise pollution, improve microclimates, and contribute to urban aesthetics. Additionally, it addresses the social and psychological advantages of integrating these green systems into urban design, emphasizing their potential to enhance the well-being and livability of city dwellers. By combining quantitative and qualitative methods, the study aims to provide a holistic understanding of the benefits and challenges associated with these innovative urban green solutions. In conclusion, this paper underscores the pivotal role of vertical green landscape facades as a sustainable and aesthetically pleasing means of combatting the environmental and social challenges of high-density urbanization. By presenting empirical evidence of their efficacy and positive reception, it advocates for their increased integration into urban planning and design strategies as a pragmatic response to the complex issues faced by contemporary cities.

Exploring Urban Compactness and Greenhouse Gas Emissions in the Road Transport Sector: A Case Study of Big Cities in South Korea

This study examined the relationship between urban compactness and greenhouse gas (GHG) emissions in the road transport sector in South Korea, focusing on 84 cities, particularly 27 metropolitan areas with populations of approximately 500,000. We developed an urban compactness index (UCI) using Moran’s I, entropy, and the Gini coefficient, integrating city size into the analysis. Cities were categorized into five groups based on their size to analyze GHG emissions and regional variations in compactness comparatively. Our results revealed a significant inverse relationship between UCI and per capita road transport GHG emissions, which was more pronounced in larger cities. Specifically, cities with a population over 1 million displayed reduced per capita road transport GHG emissions in compact urban structures. In conclusion, these findings suggest that larger cities can effectively reduce per capita road transport GHG emissions through urban planning for compact development. Additionally, planners need to consider city size when analyzing the UCI and formulating urban planning strategies aimed at achieving carbon neutrality.

Research on Urban Building Parametric Modelling Method Based on CityEngine

With the advancement of technology and the development of cities, urban planning and management methods are also constantly improving. From paper-based assignments to modern digitization, new technologies have enabled more efficient design and management for cities. 3D modeling can used to simulate the urban environment, which can assist in urban planning and management. However, large-scale modeling cannot be achieved through existing modeling methods, and there are still some shortcomings in the maintenance of the model. Therefore, this article proposes a Computer Generated Architecture (CGA) parametric 3D modeling method based on CityEngine. Research on expanding and customizing modeling rules to create indoor and outdoor modeling rule templates for buildings and methods for generating urban 3D models have been carried out. The results have shown that the completed model can be displayed on different platforms thanks to parameterized modeling. The model can be modified easily and directly applied to the analysis and decision-making of urban planning schemes.

Influence of urban-form and sociodemographic factors on street tree abundance transpire across scales in Houston, TX

Benefits provided by street trees can be enjoyed by all urban residents but trees along these public rights-of-way are usually unevenly distributed in a city. Both urban-form and sociodemographic factors can influence the spatial distribution of street trees. However, little is known how the relative importance of urban form and sociodemographic characteristics on street tree abundance inequalities vary across neighborhoods. In this study, we explored spatially varying influences of urban-form and sociodemographic variables on the distribution of street trees across Houston, Texas. We used three measures (green view index, street tree canopy, and street tree density) to measure street tree abundance. We then built multiscale geographically weighted regression (MGWR) models to capture the spatial heterogeneity in the influence of urban form and sociodemographic factors on street tree abundance. Our analysis indicates that the effects of urban-form and sociodemographic determinants on street tree abundance disparities operate at varying spatial scales across Houston. Overall, ‘building coverage ratio’ and ‘percent residential land use’ play primary roles in shaping the distribution of street tree abundance in east Houston while effects of “percent renter occupied” and “median house value” are more pronounced in west Houston. Our results also show that urban-form and sociodemographic factors interact with each other at spatial scales ranging from a few neighborhoods to several districts to the entire city. These scale- and location-specific nuances in our findings provide important insights to develop the kinds of urban planning strategies to attain increasingly equitable distribution of street tree abundance across an urban area.

Make Way for the Wind—Promoting Urban Wind Corridor Planning by Integrating RS, GIS, and CFD in Urban Planning and Design to Mitigate the Heat Island Effect

Under the trend in climate change, global warming, and the increasingly serious urban heat island effect, promoting urban wind corridor planning to reduce urban temperature and mitigate the effect of urban heat islands has received widespread attention in many cities. With emerging awareness of the need to explicitly incorporate climate considerations into urban planning and design, integrating current spatial analysis and simulation tools to enhance urban wind corridor planning to obtain the best urban ventilation effect has become an increasingly important research topic in green city development. However, how to systematically carry out urban wind corridor planning by employing related technology and simulation tools is a topic that needs to be explored urgently in both theory and practice. Taking Zhumadian City in China as an example, this study proposes a method and planning approach that uses remote sensing (RS), geographic information system (GIS), and computational fluid dynamics (CFD) in an integrated way to understand urban landscape and to conduct urban wind corridor planning. The research results reveal that the urban form of Zhumadian City favors the development of urban wind corridors, and that the railway lines and some major roads in the city have the potential to be developed as the city’s main wind corridors. However, there are still ventilation barriers resulting from the existing land use model and building layout patterns that need to be adjusted. In terms of local-level analysis, the CFD simulation analysis also reveals that some common building layout patterns may result in environments with poor ventilation. Finally, based on the results of our empirical analysis and local planning environment, specific suggestions are provided on how to develop appropriate strategies for urban wind corridor planning and adjustments related to land use planning and building layout patterns in order to mitigate the impact of the urban heat island effect.

Air quality and urban climate improvements in the world’s most populated region during the COVID-19 pandemic

In this study, we assessed air quality (AQ) and urban climate during the mobility restrictions implemented in the Greater Tokyo Area, Japan, the world’s most populated region, in response to the COVID-19 pandemic. Observations from dense surface networks were analyzed using an interpretable machine learning approach. In parallel with a ∼50% reduction in mobility and an altered lifestyle of the population, we found limited reductions in nitrogen dioxide; decreases in fine particulate matter not entirely driven by local mobility; minor variations in ozone, with a positive (negative) tendency in areas with high (low) emissions; a decrease in air temperature consistent with mobility; and pollution levels and air temperature changes with well-defined, common spatiotemporal patterns. Specifically, cooling mainly occurred in urbanized areas with an improved AQ. Overall, although reductions in mobility were moderately effective in improving the typical indicators of urban AQ, including those known to negatively impact human health, the reductions in waste heat had a stronger impact on Tokyo’s urban heat island, suggestive of a strategy to minimize exposure to heat stress. These findings can help guide urban planning strategies and policies aimed at addressing climate change.

An Americas story: hemispheric perspectives on postwar urban renewal

ABSTRACT It is commonly assumed that urban renewal in the United States following World War II was a home-grown solution applied to cities suffering from the departure of residents, retail, and capital investment as a result of suburbanization led by the White middle class. This essay argues that influences from abroad, particularly from Latin America, were also crucial to how urban renewal evolved over time from the late 1940s into the 1970s. Simultaneously, U.S.-American strategies of urban planning helped shape Latin American cities. The essay focuses on a prominent urban redeveloper of the era, Edward J. Logue, and the circle of like-minded planners with whom he interacted over his long career. As a result of their involvements in the developing world, similar modernist planning schemes and architectural structures appeared on both sides of the U.S. border, until pushback from communities during the 1960s challenged the lack of attention to local cultures and materials and to community participation in planning. Attacks on modernization theory, not least by the dependency theory popularized by Latin Americans, undermined the hegemony of universalistic modernist schemes for a time, until neoliberalism facilitated a resurgence of less regulated and restrained private interests.

Central areas in dispute: a look at the dynamics of space production in times of pandemic and its consequences

The aim of this paper is to reflect on the processes of production and re-signification of the central areas of Brazilian cities during a period of social isolation that required the reformulation, albeit temporary, of ways of socializing and consuming goods and services, as well as the creation of new strategies for urban planning and social control. During the New Coronavirus pandemic, between 2020 and 2022, urban centralities, which are usually dense and full of vitality, characterized by intense flows of people and vehicles and the convergence of interests, experienced an exceptional period. Emptied of some of their historic daily functions, Brazil's central areas, rediscovered by the real estate market as a privileged locus for the reproduction of capital since the 2010s, have received the attention of important space-transforming agents during the pandemic. The paper presents some of the transformations unleashed during this period in the traditional central area of the city of Recife, in its historic sites and surroundings, and ponders how these interventions can have repercussions on the transformation of the landscape, the social fabric and the dynamics of use of these areas.

Urban environment influences on stress, autonomic reactivity and circadian rhythm: protocol for an ambulatory study of mental health and sleep.

Converging evidence suggests that urban living is associated with an increased likelihood of developing mental health and sleep problems. Although these aspects have been investigated in separate streams of research, stress, autonomic reactivity and circadian misalignment can be hypothesized to play a prominent role in the causal pathways underlining the complex relationship between the urban environment and these two health dimensions. This study aims at quantifying the momentary impact of environmental stressors on increased autonomic reactivity and circadian rhythm, and thereby on mood and anxiety symptoms and sleep quality in the context of everyday urban living. The present article reports the protocol for a feasibility study that aims at assessing the daily environmental and mobility exposures of 40 participants from the urban area of Jerusalem over 7 days. Every participant will carry a set of wearable sensors while being tracked through space and time with GPS receivers. Skin conductance and heart rate variability will be tracked to monitor participants' stress responses and autonomic reactivity, whereas electroencephalographic signal will be used for sleep quality tracking. Light exposure, actigraphy and skin temperature will be used for ambulatory circadian monitoring. Geographically explicit ecological momentary assessment (GEMA) will be used to assess participants' perception of the environment, mood and anxiety symptoms, sleep quality and vitality. For each outcome variable (sleep quality and mental health), hierarchical mixed models including random effects at the individual level will be used. In a separate analysis, to control for potential unobserved individual-level confounders, a fixed effect at the individual level will be specified for case-crossover analyses (comparing each participant to oneself). Recent developments in wearable sensing methods, as employed in our study or with even more advanced methods reviewed in the Discussion, make it possible to gather information on the functioning of neuro-endocrine and circadian systems in a real-world context as a way to investigate the complex interactions between environmental exposures, behavior and health. Our work aims to provide evidence on the health effects of urban stressors and circadian disruptors to inspire potential interventions, municipal policies and urban planning schemes aimed at addressing those factors.

The Application of Geographic Information System in Urban Forest Ecological Compensation and Sustainable Development Evaluation

Urban forests can alleviate the urban heat island effect, improve air quality, and improve residents’ mental health. By studying urban forests, these resources can be better used and managed to create more livable urban environments. Therefore, the urban forest in the Taishan region is taken as the research object, and the ecological compensation and sustainable development of urban forest in Tai’an City are deeply analyzed by GIS. It divided the area into forest land, water bodies, wetlands, grasslands, and shrubs as the basic ecosystem types. And through secondary interpretation and combination, a complete urban forest information database was established. To evaluate the comprehensive benefits of urban forests, the analytic hierarchy process was utilized to establish a corresponding evaluation index system. Based on the assessment outcomes of the comprehensive benefits of urban forests in the area, a standard accounting method for urban forest ecological compensation was proposed. The results showed that each index of the comprehensive benefits of urban forests and the random consistency ratio were both less than 0.1. This indicated that the matrix calculation results of various indicators of urban forest comprehensive benefits had good consistency. At the target level, the comprehensive evaluation score of urban forests in the study area was 7.69. At the factor level, the weight value of the urban forest landscape structure was 0.675, and the comprehensive score was 7.62. The weight value of urban forest comprehensive benefits was 0.325, and the comprehensive score was 7.82. The quantitative weight value of urban forest greening in the study area was 0.6138, with a comprehensive score of 7.57. Based on the analysis of the issues in urban forests and ecological compensation in the research area of Tai’an City, corresponding ecological compensation strategies have been proposed. It is of great value to study the urban forest of Tai’an city, which can help to formulate more effective urban planning and sustainable development strategies. The research results can also provide a valuable reference and inspiration for the improvement of urban forest ecological environment and biodiversity protection in other areas.

INSECURITY AND TERRORISTS’ THREATS OF ATTACKS ON SELECTED NIGERIAN CITIES: IMPLICATIONS ON LAGOS RESIDENTS’ CONCERNS FOR SAFETY AND THE CITY SECURITY PLANNING

Terrorism is common but limited to certain towns in Nigeria. However, the nomenclature seems to be changing as security intelligence has it that terrorist groups are planning attacks targeting Lagos, and other notable cities. This study therefore examines concerns for safety among residents and implications on individual and city-level security planning in Lagos. The official wards as demarcated by the Independent National Electoral Commission represent clusters from which at least a respondent was randomly selected. The study’s respondents were selected from 49 (one of every five wards {20%}) wards out of 245 wards in Lagos. In the selected wards, at least two respondents were randomly selected. A total of 288 residents participated in the survey, but, only 134 respondents accurately completed the questionnaire used in this analysis, representing a 58.7% response rate. Results show that 78% of the respondents were concerned about their safety while some 90% took precaution by avoiding certain places and activities. Findings show significant relations between awareness of the planned attacks, concerns for safety, and precautionary behaviour among respondents. Besides, results show that respondents’ socio-economic characteristics, neighbourhood environmental design, and past crime victimisation mediate concerns for safety and security behaviour. The study concludes that the emergence of this security intelligence in the public domain has further contributed to the increasing fear and residents’ mobility change. The study recommends among others policing strategies, a new urbanism, where urban planning and design strategies are applied to make attacks more difficult to carry out in soft spaces and places.

Technological innovations in mitigating winter health challenges in New York City, USA

This review paper examines the role of technological innovations in mitigating winter health challenges in New York City (NYC). The primary objective is to analyze how emerging technologies are integrated into public health strategies to address the unique health risks posed by the winter season in one of the world's most populous urban environments. The methodology involves a comprehensive literature review focusing on recent advancements in technology within the context of public health and urban planning. Key sources include peer-reviewed articles, case studies, and reports on smart city initiatives, climate change impacts, and the implementation of health technologies in NYC. Key findings reveal that the integration of smart city technologies, such as advanced data analytics, IoT devices, and AI-driven solutions, has significantly improved healthcare delivery and emergency response during winter. However, challenges in implementation, particularly in under-resourced settings, highlight the need for tailored, context-driven technological solutions. The impact of climate change on winter health dynamics underscores the importance of innovative urban planning and public health strategies. The potential of emerging technologies, including nanotechnology for air purification and spatial analysis of health data, offers promising avenues for improving public health in urban settings during winter. The review suggests that technological innovations play a crucial role in enhancing the capacity of NYC to manage winter health risks. It recommends increased investment in smart city technologies, support for under-resourced healthcare settings, and the development of climate change adaptation strategies. The evolution of healthcare in winter contexts is increasingly being shaped by these technological advancements, paving the way for a more resilient and sustainable approach to public health in urban environments.