Shima Hamidi

Relationship between urban sprawl and physical activity, obesity, and morbidity - update and refinement.

AIMS This study aims to model multiple health outcomes and behaviors in terms of the updated, refined, and validated county compactness/sprawl measures. METHODS Multiple health outcomes and behaviors are modeled using multi-level analysis. RESULTS After controlling for observed confounding influences, both original and new compactness measures are negatively related to BMI, obesity, heart disease, high blood pressure, and diabetes. Indices are not significantly related to physical activity, perhaps because physical activity is not defined broadly to include active travel to work, shopping, and other destinations. CONCLUSIONS Developing urban and suburban areas in a more compact manner may have some salutary effect on obesity and chronic disease trends.

Compactness versus Sprawl A Review of Recent Evidence from the United States

In 1997, the Journal of the American Planning Association published a pair of point–counterpoint articles now listed by the American Planning Association as “classics” in the urban planning literature. In the first article, “Are Compact Cities Desirable?” Gordon and Richardson argued in favor of urban sprawl as a benign response to consumer preferences. In the counterpoint article, “Is Los Angeles-Style Sprawl Desirable?” Ewing argued for compact cities as an alternative to sprawl. It is time to reprise the debate. This article summarizes the literature on urban sprawl characteristics and measurements, causes, impacts, and remedies since the original debate.

The typology of the American metropolis: monocentricity, polycentricity, or generalized dispersion?

ABSTRACT Although the spatial structure of employment in large US metropolitan regions is a well-researched topic, few studies focus on medium-sized and small US metropolitan regions. Consequently, there is no overall typology relating small-to-medium urban form to employment distribution. We address this gap by investigating the spatial structure of employment in 356 metropolitan regions. We conceptualize six typologies based on three categories that have overlapping properties: “monocentricity,” “polycentricity,” and “generalized dispersion.” The study has three main findings. First, the three types of urban form that we identify as “hybrid” outnumber the three “pure” types by almost four to one. Second, job dispersion is a dominant characteristic in almost 70% of all metropolitan statistical areas (MSAs) (including the hybrid types), and polycentricity (56.7% of MSAs) is somewhat more common than monocentricity. Third, there is a strong relationship between population size and density. The population of medium-sized metropolitan areas is generally more dispersed than that of small and large metropolitan areas. Polycentricy emerges mostly in large metropolitan regions, while monocentrity is found in both small and large metropolitan regions.

Compact development and VMT—Environmental determinism, self-selection, or some of both?

There is a long-running debate in the planning literature about the effects of the built environment on travel behavior and the degree to which apparent effects are due to the tendency of households to self-select into neighborhoods that reinforce their travel preferences. Those who want to walk will choose walkable neighborhoods, and those who want to use transit will choose transit-served neighborhoods. These households might have walked or used transit more than their neighbors wherever they lived. Most previous studies have shown that individual attitudes attenuate the relationship between the residential environment and travel choices, and so the effect of the built environment on travel may be overestimated. But there are other researchers who argue the reverse, claiming that residential preferences reinforce built environmental influences. This study assesses the relative importance of the built environment and residential preferences/travel attitudes for a sample of 962 households in the Greater Salt Lake region using structural equation modeling. For the sake of simplicity, we extracted two factors using principal component analysis, one representing the built environment and the other representing residential preferences/attitudes. Our findings are consistent with the view that the neighborhood built environment and residential preferences both influence household’s travel, that the built environment is the stronger influence, and that the built environment affects travel through two causal pathways, one direct and the other indirect, through attitudes.

The Cost and Affordability Paradox of Transit-Oriented Development: A Comparison of Housing and Transportation Costs Across Transit-Oriented Development, Hybrid and Transit-Adjacent Development Station Typologies

Abstract This study presents a comparison of housing and transportation costs (H+T) in 4,399 fixed-route transit station areas across the United States. Each station area is classified as a transit-oriented development (TOD), hybrid, or transit-adjacent development (TAD) based on walkability and housing density targets. Station areas with a Walk Score of 70 or greater and a gross housing density of 8 units per acre or more are classified as TOD. Station areas that meet just one of these criteria are classified as hybrids, and those that do not meet either of these criteria are categorized as TAD. The findings reveal a paradox that whereas TOD are more expensive places to buy and rent housing, they are more affordable than hybrids and TAD because the lower cost of transportation offsets housing costs. We argue that policies to increase the density and walkability of hybrid and TAD station areas, which account for two thirds of all station areas across the United States, should be a top priority for both housing and transportation officials.

Obesity and the built environment at different urban scales: examining the literature.

The majority of people now live in an urban (or suburban) environment. The built (material) environment, its vehicular and pedestrian infrastructure, buildings, and public realm places, are the places used for working, living, and recreating. The environment currently favors and facilitates motorized vehicles generally, and private automobiles especially. The prioritization given to vehicles reduces opportunities for other, more active modes of travel such as walking and bicycling. Though the built environment cannot be said to directly affect human obesity, the built environment clearly has a relationship to obesity as a consequence of physical activity. Most concerning is that rates of obesity have risen as cars have become increasingly privileged, leading to places that favor driving over walking or bicycling. This review examines current empirical literature on the environment and obesity at 3 key urban scales: macro, meso, and micro. Other key issues examined include longitudinal studies and self-selection bias. Evidence for a relationship between urban and suburban environments and obesity is found in the literature, but the lack of longitudinal research and research controlling for self-selection bias remains underrepresented.

Does urban form matter for innovation productivity? A national multi-level study of the association between neighbourhood innovation capacity and urban sprawl:

Geography of innovation, creative clustering, urban buzz and innovation districts are place-based concepts that have emerged as a result of the US economy’s transformation to knowledge-intensive economies. The notable built environment characteristics of these concepts are spatial clustering, walkability and proximity to urban amenities, diversity, regional connectivity and agglomeration. While several of these characteristics have been associated with urban sprawl in previous studies, there is a lack of direct evidence on how urban sprawl affects innovation productivity. This national study seeks to examine the relationship between urban sprawl, place-based characteristics and innovation productivity. We used Multilevel Modelling to account for built environment characteristics at both neighbourhood and regional levels. We found that innovative firms tend to locate more in census tracts that are less compact but offer spatial proximity to firms in related business sectors. This is likely due to the higher land and property value in compact areas, which could make it unaffordable for small businesses. We also found that the regional compactness positively and significantly affects the number of innovative firms. This is likely due to the role of compact regions in supporting public transit investments, enhancing social capital and reducing poverty and racial segregation.

Testing Newman and Kenworthy’s Theory of Density and Automobile Dependence:

This study tests four hypotheses related to the much-cited work on density and automobile dependence by Newman and Kenworthy, using multivariate analysis and data for 157 large US urbanized areas. We find that density alone explains only a small fraction of the variation in vehicle miles traveled (VMT), and many confounders account for the differences in automobile dependence. We also find that it is not the localized density of individual neighborhoods that causes VMT to be lower in compact urbanized areas but rather the relative accessibility of neighborhoods to the rest of the region.

Value of Transit as Reflected in U.S. Single-Family Home Premiums: A Meta-Analysis

Although transit accessibility premiums have been rigorously studied at the local and regional levels for more than 40 years, drawing conclusions about premiums on a national scale requires a meta-analysis. Estimating effect size is a primary purpose of a meta-analysis. Effect size was calculated in 2007 by using pre-2003 studies but has not been studied since. This study sought to fill gaps in the literature by conducting a regression analysis and a thorough meta-analysis that reviewed 114 studies published from 1976 to 2014. Of 114 U.S. and Canadian single-family studies, a sample of 45 single-family studies was selected for further analysis. Compared with the previous meta-analysis, the current analysis found that, overall, U.S. and Canadian studies reported lower premiums on average for single-family houses. The average single-family home premium of 2.3% was significantly lower than the 4.2% premium calculated by the previous meta-analysis. It was found that reported transit premiums were decreasing over time as more variables, such as walkability of station areas, were statistically controlled. It was also found that compact regions with greater accessibility via transit produced higher transit premiums and transit premiums were neutral with respect to technology (light versus heavy rail) once regional compactness was controlled for. These findings suggest that to get the most out of transit investments, planners and public officials must make an effort to create compact regional development patterns and that single-family housing may not be the best use in areas close to transit.

Quantifying Transit’s Impact on GHG Emissions and Energy Use—The Land Use Component

This report analytically examines the complex interrelationships between transit and land use patterns to better understand their contribution to compact development and the resulting greenhouse gas (GHG) reduction benefits. The report is accompanied by an Excel-based sketch-modeling tool (“calculator tool”) that applies the research findings. The calculator tool estimates the land use benefits of existing or planned transit projects with a minimum amount of input data required. The report presents transit’s impact on GHG emissions and energy use, including both the ridership effects and the land use effects; introduces and provides a user’s guide to the calculator tool; identifies future research; and includes two technical appendices pertaining to the use of statistical models in this research. This research will be useful to transit agencies, planners, modelers, and researchers seeking to better understand and to quantify the impacts of transit service on compact development, energy use, and air quality in urbanized areas.