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Title:The role of urban spatial structure in reducing VMT and GHG emissions
Author(s):Lee, Sungwon
Director of Research:Lee, Bumsoo
Doctoral Committee Chair(s):Lee, Bumsoo
Doctoral Committee Member(s):Deal, Brian; Wilson, Beverly; Hewings, Geoffrey J.D.
Department / Program:Urban & Regional Planning
Discipline:Regional Planning
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Sustainable Urban Spatial Structure
Built Environment
Land Use Change
Geographic Scale
Travel Behavior
Residential Energy Consumption
Greenhouse Gas Emissions (GHGs)
Abstract:The aim of this study is to uncover the role of urban spatial structure in greenhouse gas (GHG) mitigation and to understand how sustainable urban form can better reduce climate change. Until now, a great number of studies have focused on the links between urban spatial structure and travel behavior, but little is known about spatial structure impacts on residential energy consumption. Most previous studies applied the use of neighborhood scale spatial structure to understand greenhouse gas emissions. However, such studies are too narrow to explain total urban spatial influences. This dissertation research therefore focuses on regional scale spatial structure (urban area level) in order to decrease GHGs and mitigate climate change. In doing so, this dissertation research consists of the three specific topics to scrutinize the role of sustainable urban spatial structure. The first topic (chapter 2) empirically examines whether and to what extent spatial structure affects the amount of household sector greenhouse gas emissions in U.S. urbanized areas. The study covers the comprehensive impacts of spatial structure not only on travel behavior, but also on residential energy consumption. Therefore, we can trace the overall impacts of urban spatial structure on all sources of GHG in the US household sector. The second topic (chapter 3) focuses on the impact of multiple geographic scales of sustainable built-environment to mitigate GHGs. In the study, the impacts of neighborhood level characters and regional level urban form elements are compared. The final topic (chapter 4) compares land-use policy with price policy to effectively reduce GHGs, and empirically shows how both policies can support GHG mitigation. 1) The influence of urban form on greenhouse emissions in the household sector This study comprehensively investigates the diverse paths through which urban form influences an individual household’s carbon dioxide emissions in the 125 largest urbanized areas in the U.S. This research takes a consolidated approach in investigating all energy consumption in the household sector: CO2 emissions from heating, cooling and transportation. The result of the multilevel structure equation model (multilevel SEM) analyses shows that doubling population-weighted density is associated with a reduction in CO2 emissions from household travel and residential energy consumption by 48% and 35%, respectively. The impacts of a centralized population and a polycentric structure have only a moderate impact in the analyses. The result also shows that doubling per capita transit subsidies is associated with a nearly 46% lower VMT and 18% reduction in transportation CO2 emissions. Given that household travel and residential energy use account for 42% of total U.S. carbon dioxide emissions, these research findings corroborate the notion that urban land use and transportation policies to build more compact and transit friendly cities should be a crucial part of any strategic efforts to mitigate GHG emissions and stabilize climate at all levels of government. 2) Sustainable urban form at local and regional scales The link between urban form and travel behavior is recognized as a key role in understanding the role of sustainable urban development in reducing greenhouse gas emissions in the transportation sector. Many recent studies have found that urban form variables—such as density, land use diversity, street design, destination accessibility, and distance to transit (the “5Ds”)—significantly influence travel behavior including mode choice, trip frequency, trip distance, and ultimately vehicle miles traveled (VMT), and they are regarded as the fundamental principles for land use policies to promote more sustainable transportation. In previous study, the 5 element impacts on VMT (VMT elasticity w.r.t. 5Ds) are significant, but not large. The reason seems to come from the small geographic unit of analysis (census tract, census block group or TAZ level). According to the NHTS (2009), more than 85% Americans still use automobile when they travel, and the average one-way trip distance by auto is about 9 miles, while the average radius of census tract and census block group is only about 0.5 and 0.3 miles, respectively. Moreover, many sustainable urban form studies have focuses on neighborhood character based on residence or working place, but home based work (HBW) is less than 10%, and there are various trip purposes, so there are diverse origins and destinations in each travel. Ironically, however, most studies suggest that coupling sustainable urban structure with supporting neighborhood structures decreases VMT, but most people use cars for travel for trips beyond the geographic unit of analysis. To fill the gap in the literature, this study investigates the influences of urban form at both geographical scales on travel behavior and carbon dioxide emissions using a multilevel analysis (3 level analysis; individual household, neighborhood, and urbanized area). The results show that the influence of regional level urban form is higher than that of neighborhood level on VMT. Regional level variables such as population weighted density (PWD), population centrality, jobs-to-housing ratio, and transit service supply significantly reduce VMT and CO2 from transportation sector. Most 5D elements at the neighborhood level also significantly diminish VMT and CO2, but the coefficient of regional level variables are higher than that of neighborhood level urban form elements. Moreover, the empirical outputs indicate that the positive effects of sustainable urban elements (5Ds) at the neighborhood level to reduce GHGs are increased under more high-density, high-centralized, and high job accessible UAs than auto-oriented UAs. For instance, when we double the compactness level at the neighborhood level, VMT decreases by about 50% in the average PWD UAs such as St. Louis. However, the influence can intensify by about 75% when the UA density (PWD) arrives at the New York level. 3) Complementarity between land use planning and pricing in VMT reduction To effectively reduce VMT, there seems to be no majority consensus. There is a wide gap between advocates of pricing policies and advocates of land use planning. Advocates of each approach underestimate the role and impacts of the other approach. In particular, skepticism still remains concerning the potential for more sustainable urban form and development patterns in reducing VMT and carbon emissions. The majority planners, on the other hand, emphasize that “getting prices right” policies cannot be effective in the absence of alternatives to automobile usage in many U.S. cities. However, land use planning and pricing approaches are complementary and potentially synergetic rather than competing and conflicting. Further, all possible policy options should be fully employed to achieve climate-stabilizing GHG reduction targets. Thus, policy analysts and decision makers should understand the complex interactions between various policy instruments to mitigate policy conflicts and maximize synergetic effects. Nonetheless, empirical research on the policy synergy between different approaches in transportation planning is extremely rare. To enhance the understanding of the policy synergy between pricing and land use planning approaches, this study examines the interaction effects between fuel prices and land use (urban form) variables in reducing VMT in 115 UAs for 10 years from Jan. 2002 to Dec. 2011 (monthly data). To find the both policy impacts, diverse empirical analyses are conducted from simple comparative analysis, to regression analysis, panel analysis, and panel type locally weighted smoothing (P-LOESS). The results show that there are synergic effect between land use policies and fuel price policies. Under the high fuel price, VMT reducing impacts of most compact urban form variables (UA level) are estimated to be stronger. When PWD doubles, VMT is reduced by about 19% under around 1 dollar per gallon ($ 2005), but the impact increases to about 27% under about $2.5 /gallon. However, the complementary relations do not seem constant as gasoline price increases. With gasoline price increases, the elasticities of VMT dramatically increases below $2.5 per gallon. However, the elasticities remain at around 27%, even when the fuel price increases beyond $2.5 to $4 per gallon. The elasticities of urban compactness and centrality also show a similar pattern, in which they stabilize at a certain level. The implications of all findings from the three topics may greatly add to sustainable land use policy and transportation planning. While current federal- and state-level climate change policies mainly depend on technology solutions, the first study gives strong evidence for the importance of land use planning, as GHG mitigation strategies must alter travel behavior as well as energy consumption behavior. The comparison between local and regional level built environment impacts in the second topic highlight an essential issue of whether the state and/or regional governance can effectively reduce GHGs. The study shows that scattered and fragmented development of compact neighborhoods is not sufficient to moderate auto-oriented travel behavior. Instead, the study implies that strategic regional level coordination of smart growth policies can effectively foster sustainable travel behavior such as urban growth boundaries, balanced jobs-housing development, and transit oriented development. The final study underlines how both land use and fuel price policies generates synergic effects, which is largely overlooked by planners. The study empirically shows the adequate range of fuel prices to stimulate increasing effectiveness of sustainable land use policy, so the results can provide great evidence for the actual implementation of synergic activities.
Issue Date:2015-11-30
Rights Information:Copyright 2015 Sungwon Lee
Date Available in IDEALS:2016-03-02
Date Deposited:2015-12

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