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Doctor of Philosophy with a Major in City and Regional Planning
Doctor of Philosophy with a Major in City and Regional Planning
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ItemA methodological assessment of extreme heat mortality modeling and heat vulnerability mapping in Atlanta, Detroit, and Phoenix(Georgia Institute of Technology, 2019-11-12) Mallen, Evan SheppardExtreme temperatures pose an increasingly high risk to human health and are projected to worsen in a warming climate with increased intensity, duration and frequency of heat waves, further amplified by the urban heat island, in the coming decades. To mitigate heat exposure and protect sensitive populations, urban planners are increasingly using decision support tools like heat vulnerability indices (HVIs) to identify high priority areas for intervention and investment. However, HVIs often capture only proxy heat exposure indicators at the land surface level, not air temperatures that humans experience, and are highly subjective in their construction methodology. This gap can be filled using regional climate models like the Weather Research & Forecasting (WRF) model to simulate air temperatures comprehensively over a city, coupled with a heat exposure-response function to objectively estimate mortality attributable to heat. But this method is often beyond the capabilities of local planning departments due to limitations in funding or technical expertise to run the model. Careful consideration of decision support tool selection will be an important factor in determining the future resilience of urban populations in a changing climate. Through a comparative analysis, this study investigates the relationship and utility of HVIs and spatial statistical attribution models with a focus on 1) the extent to which HVI methods can replicate spatial prioritization from a WRF-driven mortality model; 2) the relative significance of place-based vulnerabilities used in the HVI; and 3) the potential to reliably replicate a WRF-driven mortality model using publicly available datasets. This information can help urban planners and public health officials improve their emergency response plans and communication strategies for heat mitigation by specifically targeting short and long-term responses where there is greatest need. These techniques equip planners with a useful and accessible tool to protect vulnerable populations effectively and efficiently with minimal public funds and could advance the policies we use to adapt to a changing climate.
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ItemDoes green infrastructure promote equitable development? The mediating role of social capital in shaping impacts(Georgia Institute of Technology, 2019-05-17) Fisch, Jessica AnnPlanners, policymakers, and elected officials increasingly view investments in green infrastructure, parks and other green development as opportunities for spurring economic growth, increasing environmental quality, and providing social and recreational amenities in urban areas. However, research has indicated that these projects do not adequately address equity concerns, such as access for low-income and marginalized groups, housing affordability, and displacement of existing residents. Consequently, green infrastructure projects can lead to ‘environmental gentrification. While several works have argued that social capital—the building of relationships, trust, and networks of stakeholders—has the potential to promote more equitable development, the conditions under which more equitable outcomes for green infrastructure projects might be supported and the role of social capital in addressing these concerns has not been adequately examined. This study seeks to clarify the mechanisms through which green infrastructure planning might advance the development of social capital and in turn how social capital influences the housing affordability, gentrification, and community benefits aspects of green infrastructure planning and policy development. The research examines these interrelationships in Atlanta and Washington, D.C., cities with a prominent focus on planning for green infrastructure, high levels of segregation by race and income, and distinct city-wide approaches to coping with gentrification. In clarifying interactions between social capital and green infrastructure planning processes and outcomes, the research enhances our understanding of how social capital might support an increased focus on equity in green infrastructure planning. In particular, the study finds that green infrastructure planning may reinforce social capital, which in turn shapes green infrastructure projects and planning processes with regard to addressing housing affordability and community benefits concerns. It further finds that social capital has served as a catalyst for advocacy and the development of organizations, policies, and programs focused on housing affordability and workforce development. Finally, state and city-level political contexts concerning the goals and tools for promoting housing affordability and community benefits shape the ability of municipal and neighborhood-level actors to address equity concerns associated with green development. These findings support several recommendations for policy and planning to promote more equitable development surrounding green infrastructure projects and planning processes.
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ItemRed hot American summer: Extreme heat and physical activity of adults(Georgia Institute of Technology, 2018-12-20) Lanza, KevinThis dissertation investigates the relationship between extreme summer heat and outdoor, indoor, and total (i.e., outdoor + indoor) physical activity levels of US adults. With the lack of physical activity across the US, public health practitioners and city planners are making concerted efforts to promote physical activity through formal interventions and the design of spaces, respectively. To inform physical activity interventions, researchers examine which factors associate with physical activity, one of which is temperature. The majority of studies exhibit a significant positive association between temperature and physical activity, yet no studies examine exceptionally hot summer days, which disproportionately impact cities and are set to become more prevalent in the future. This dissertation tests three novel questions: 1) how do hot days associate with outdoor, indoor, and total physical activity; 2) how do hot days influence the effect of built environment factors on outdoor physical activity; and 3) how do heat waves – consecutive hot days – associate with outdoor, indoor, and total physical activity? This work made use of self-reported physical activity and demographic data collected during summer 2016 for a National Science Foundation project (NSF award number: 1520803). The study sample included a spatial and demographic mix of ~50 adults per study city (i.e., Atlanta, Detroit, and Phoenix). Heat was measured as both hot days and heat waves (i.e., two or more consecutive hot days), utilizing air temperature and relative humidity data collected at each city’s major airport. The examined built environment factors (i.e., density, safety, trees, hilliness, connectivity, access to parks, and access to shops + services) were primarily collected from government sources and calculated within an 800m Euclidean distance of each study participant’s home address. Separate two-level growth curve models were run for each research question, version of the dependent variable (i.e., Any Activity and Recommended Activity), and location of physical activity (i.e., outdoor, indoor, and total). Multilevel modeling predicted that 1) hot days do not exhibit a significant association with indoor, outdoor, or total physical activity; 2) hot days do not significantly influence the effect of built environment factors on outdoor physical activity; and 3) heat waves do not exhibit a significant association with outdoor, indoor, or total physical activity. These findings refute the study hypotheses that extreme summer heat would decrease outdoor and total physical activity, while shifting physical activity to indoor, thermally comfortable environments. With high temperatures potentially not serving as a barrier to physical activity, cities should allocate resources to reducing the risk of exertional heat illness, an adverse health event expected to become more frequent with physical activity promotion and climate change.
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ItemWhat metropolitan-level factors affect Latino-owned business performance?(Georgia Institute of Technology, 2018-11-07) Doyle, Jessica L. H.An estimated 1.54 million Latinos are self-employed in unincorporated businesses, while the 2012 national Survey of Business Owners counted 3.3 million Latino-owned firms, with a total of $474 million in annual sales or receipts. This entrepreneurship is all the more remarkable given that Latinos traditionally begin their businesses with lower levels of personal capital and have historically had more difficulty obtaining formal startup capital from third parties such as banks or government agencies. While this observation holds true at the national level, different metropolitan areas may provide business environments more or less hospitable to Latino-owned businesses, due to such factors as industry mix, availability of financing, demographics, and local political expression of “welcoming” or anti-immigrant sentiment. This dissertation examines the question of what metropolitan-level factors affect Latino-owned business formation and performance. It finds that Latino entrepreneurs nationwide face persistent obstacles in the form of obtaining financing for both new and existing businesses, which can be addressed at the local level. However, certain concepts currently prominent in research about ethnic entrepreneurs, such as the makeup and geographic concentration of the “ethnic enclave” and the importance of prior history of immigrant settlement in the metropolitan area, may be less applicable to Latinos who come from a broader range of countries and settle in less dense metropolitan areas.
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ItemWill millennials stay in cities and travel without cars?(Georgia Institute of Technology, 2018-08-24) Lee, YongsungWill millennials stay in cities and travel without cars? To answer this question, this dissertation examines heterogeneity in modality styles and residential preferences in a sample of millennials and members of Generation X in California in 2015. It finds that both sociodemographic/ economic characteristics and attitudes about various dimensions (e.g., preferred built environments, travel modes, and car ownership) account for the heterogeneous behavioral and choice patterns in the sample. These findings provide insights on the ways millennials may switch their modality styles or residential preferences in response to changes in sociodemographic/economic conditions or attitudes in the coming years. This dissertation highlights the use of latent-class approaches as effective for the identification of heterogeneity in tastes related to the travel behaviors and location choices of millennials. Researchers are advised to apply these approaches to longitudinal analyses. This research also informs planners and policymakers of dynamic changes in the form or share of latent classes in their region.
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ItemInvestigating the potential of on-demand ride service and its impact on mode choice and accessibility(Georgia Institute of Technology, 2018-07-31) Wang, FangruThe recent advancement in information technologies has facilitated the emergence and growth of travel modes like ride-sourcing, car-sharing, and bike-sharing, providing travelers with unprecedentedly broad travel options. The nature of these options will significantly affect the way how people travel and engage in activities, and therefore lead to transport network impacts. Ride-sourcing, referring to app-based on-demand ride service (ODRS), exhibits similar traits of traditional taxis but provides better real-time information and lowered cost compared to taxis. The fast growth of ride-sourcing also reflects the trend known as Mobility as a Service (MaaS) and can be seen as a litmus test of connected and autonomous vehicles which will further transform the transportation landscape. This dissertation explores three main aspects of ODRS using a three-part analysis: an exploratory analysis of the role of ODRS in urban transportation, a discrete choice modeling to understand the choice of ODRS, and scenario forecasting to quantify the potential impact of ODRS on transport accessibility and equity. The dissertation results indicate the critical role that ODRS has in serving transport-disadvantaged population and multimodal travel and filling in gaps of transit, identify the socio-demographic, built environment, and trip characteristics associated with the choice of ODRS, and reveal the substantial accessibility and equity benefits of integrating ODRS with transit. The dissertation also shows strong performance of machine learning travel mode choices and suggests the further integration of machine learning with travel demand forecasting. The findings unveil the potentials of ODRS in elevating transport benefits of the existing infrastructure and point to strategies of leveraging ODRS and autonomous vehicles to improve transport mobility, accessibility, and equity. The results also reveal challenges of realizing the benefits of ODRS and incorporating ODRS into travel demand forecasting, which will have to rely on data collection, public-private collaboration, and research and practical exploration of synergizing ODRS with other travel modes.
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ItemElectronic retail effects on airports and regional development(Georgia Institute of Technology, 2018-05-04) Hylton, Peter J.This dissertation is an investigation of the relationship between e-retail logistics (e-fulfillment) and aviation, and of airport staff’s planning responses to e-fulfillment. By its nature, planning requires a thorough understanding of the forces on transportation and land use that can affect areas of planning interest. Electronic retail (e-retail) is one such trend whose rapid growth influences airport activity, demand for industrial real estate, workforce needs, and surface transportation infrastructure. E-retail’s growth alters regions’ attractiveness for logistics development, the strategies needed to promote the industry, and the data and models required to prepare for its transportation, land use, and workforce needs. This study’s objective is to provide guidance to urban and airport planners on the relevant effects on e-fulfillment as well as appropriate planning responses. The dissertation includes a three-part analysis. A location model measures differences between the sales channels in the regional and airport traits associated with logistics activity. A survey of retail shippers is intended to examine associations detected in the logistics model and measure their relative strength by documenting differences in operations and regional needs between DCs and FCs. Interviews with logistics professionals supplement the shipper survey. Analysis 3 examines the extent to which airport staffs are planning for changes in cargo patterns associated with e-fulfillment through planning document reviews and interviews with staff at seven airports served by Amazon Prime Air. Dissertation results indicate that e-retailers choose FC location as a function of customer proximity, airport access, integrator hub proximity, and a variety of regional factors with weaker effects. E-retail activity will continue to generate disproportionate air cargo activity while concentrating logistics facilities in the same regions as large customer bases, integrator air hubs, and international gateway airports. These patterns will impact infrastructure and land needs, and planners should incorporate these trends into their forecasts and strategies. Airport planners are increasingly aware of e-retail’s cargo generation potential, and they are gathering data in an ad hoc manner to understand it. The dissertation concludes with a discussion of implications of the research for airport and transportation planners, economic development planners, and land use planners. Logistics activity related to e-retail is expected to grow in coming decades, concentrating particularly around logistics hubs and population centers in the Northeast, Ohio River Valley, and major metropolitan areas.
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ItemExploring urban agriculture as a climate change mitigation strategy at the neighborhood scale(Georgia Institute of Technology, 2017-08-28) Habeeb, Dana M.Extreme heat events are responsible for more annual fatalities in the United States than any other form of extreme weather. Urban centers are particularly vulnerable to the threats of excessive heat as most cities are home to large populations of lower income individuals who often lack access to air conditioning or adequate healthcare facilities. Urban populations are also more likely to be exposed to extreme heat due to the urban heat island (UHI) phenomenon. As the global population continues to urbanize, the number of vulnerable individuals will continue to increase making urban heat island mitigation strategies all the more important. In this research, I explore urban agriculture as an urban heat island mitigation strategy. I conduct a land cover analysis to investigate the climate effect of urban agriculture on local temperatures. I use satellite temperature data, land cover data, and urban form metrics to estimate how the percent change in urban agriculture impacts local temperatures. My research shows that urban agriculture decreases high nighttime temperatures during summer months, which is an important public health finding as nighttime temperatures are a better metric for capturing negative health effects from extreme heat than daytime temperatures. At the local level, an increase of 10-acres per km2 in agricultural land cover can reduce nighttime temperatures by approximately 0.65°F accounting for approximately 10% of Atlanta's UHI effect. Agricultural lands outperformed forested land cover as a nighttime cooling mechanism across the Atlanta MSA. I investigated whether the urban form of a neighborhood impacts the relationship between urban agriculture and local climate and found an interaction effect between urban agriculture and urban form when a heat wave is present. Agricultural implementations in dense urban neighborhoods decrease temperatures more than in the residential areas. Additionally, I found that a minimum of seven acres of agricultural lands must be implemented before cooling effects will occur in urban areas. Though agricultural lands can act as a successful heat mitigation strategy by lowering nighttime temperatures, during heat waves the magnitude of the cooling effect is diminished. As such, I argue for an active management strategy to ensure that urban agriculture maintains its cooling potential during extreme heat conditions. In addition, I argue that urban agriculture should not only be placed in cities but that the morphology of the built environment should be taken into consideration when selecting locations for urban agriculture. When designing heat mitigation strategies, it is important for planners and policy makers to quantify the difference between vegetative approaches in order to understand the tradeoffs they are making climatically, environmentally, and socially. As such the results of my research can help guide planners when selecting between vegetative UHI mitigation strategies and may further support the burgeoning urban agriculture movement.
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ItemThe impact of racial segregation, income sorting and risk-based mortgage pricing on housing wealth inequality: A comparison between urban regions in the United States(Georgia Institute of Technology, 2017-05-25) Raymond, EloraHousing wealth is the cornerstone of U.S. households’ balance sheets and is among the largest stores of wealth in the United States. This study examines rising housing wealth inequality between 2005 and 2015 in an urban context. Past research suggests that rising income inequality, rising income segregation, or racial segregation could be a cause. Other research highlights the role of mortgage lending in generating inequality. The subprime and foreclosure crises have a well-documented association with housing inequality. Other work highlights risk based mortgage pricing more generally as a mechanism for widening inequality. I first examine the drivers of urban housing wealth inequality with a cross-sectional regression analysis in 2000-2005. I examine how income and racial segregation affect housing wealth inequality between cities prior to the crisis, and find that income inequality is weakly correlated with housing wealth inequality, but income and racial segregation have strong effects. Then, I examine if changes in segregation explain rising housing wealth inequality during the real estate and financial crises of the 2000s, or if mortgage market factors explain the rise. I find that changes in income inequality lead to higher housing wealth inequality; that rises in Black racial segregation again explain much of the increase, and that subprime lending does not fully account for that effect. Finally, I use granular data in a series of quantile regressions to understand the drivers of housing wealth inequality during the housing market recovery years of 2010-2015. I find that risk-based mortgage pricing and income segregation interact to produce significant and meaningfully large increases in housing wealth inequality over a 5-year period, from 2010-2015. Finally, I briefly discuss the ramifications for national housing finance reform, as well as for state and local mortgage programs and policies like inclusionary/exclusionary zoning. The current administration has put housing finance reform at the top of its agenda. Many proposals suggest partial or complete privatization of the government sponsored enterprises (GSE)s, which would lead to increase in risk-based pricing and market segmentation. Additionally, reform could disrupt GSE subsidization of state and local mortgage revenue bond programs. State and local actors should seek to preserve these capacities and increase local programs to guarantee mortgages and provide down payment assistance where possible. Cities should weigh carefully the costs of exclusionary zoning not only on income segregation, but on widening wealth inequality within their region. This dissertation contributes to the literature by situating the phenomenon of rising housing wealth inequality in a spatial, urban context and describing the impact of individual, neighborhood, and regional characteristics on the production of housing wealth inequality. I also tie these results to policy remedies at the national and local levels.
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ItemThe interaction between land use and transportation in the era of shared autonomous vehicles: a simulation model(Georgia Institute of Technology, 2017-05-19) Zhang, WenwenThe promising Shared Autonomous Vehicle (SAV) system will inevitably lead to changes in urban land use. Despite recent proliferating studies regarding SAVs, it remains unclear how this affordable and environmentally friendly travel mode will influence residential and commercial location choices and potentially transform urban form. This dissertation develops a discrete event based SAV simulation and implements the model using the transportation network, travel demand, and land use data from Atlanta Metropolitan area. The model is then integrated with residential and employment (re)location choice models to explore how the SAV system will affect urban parking, residential land use, as well as employment agglomeration patterns. The results suggest SAV can significantly reduce parking demand by over 90%. Additionally, the simulation results also indicate the system will not induce residential sprawl into rural areas. Finally, it appears that SAV will accelerate the existing deindustrialization process in cities. The results of this study can provide implications for devising more sustainable land use policies in the era of SAVs.