Grantee Research Project Results
Final Report: Metropolitan Accessibility and Transportation Sustainability: Comparative Indicators for Policy Reform
EPA Grant Number: R833349Title: Metropolitan Accessibility and Transportation Sustainability: Comparative Indicators for Policy Reform
Investigators: Levine, Jonathan , Grengs, Joe , Shen, Qing , Shen, Qingyun
Institution: University of Michigan , University of Maryland - College Park
EPA Project Officer: Hahn, Intaek
Project Period: February 1, 2007 through January 31, 2010 (Extended to January 31, 2011)
Project Amount: $300,000
RFA: Collaborative Science And Technology Network For Sustainability (2006) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , Sustainable and Healthy Communities
Objective:
Transportation planning and policy have traditionally been evaluated with mobility-based indicators. These metrics implicitly treat ease of movement ‒ often interpreted as roadway travel speeds ‒ as definitive indicators of success in transportation policy. This perspective has led to the development of highway-intensive metropolitan areas in which vehicle-miles traveled per capita are high. Apart from its environmental implications, this perspective neglects the insight that the purpose of travel is not movement but access; that is, the demand for travel is derived from people’s desires to reach destinations. Movement is only one means to achieving accessibility; the other two are proximity (when people are near to their destinations, they can reach them without much movement) and remote connectivity (e.g., via phone or Internet). The current study seeks to promote a shift in transportation policy from mobility-centered to accessibility-centered evaluation and practice by developing and estimating accessibility indicators that can be compared both within and between metropolitan areas.
Summary/Accomplishments (Outputs/Outcomes):
Accessibility is most commonly studied and measured within the context of a single metropolitan region. By contrast, this study applies metrics of accessibility (for work, non-work, by auto and transit) that incorporate both mobility and proximity to 38 of the largest 50 U.S. metropolitan areas. This cross-sectional analysis allows both intermetropolitan comparison (of accessibility overall and of the equity of its distribution) and assessment of the determinants of metropolitan accessibility.
The two components of accessibility analyzed here ‒ mobility and proximity ‒ exist in tension with each other: places with rapid surface travel are usually places where origins and destinations are far apart; places with many origins and destinations in close proximity are places where travel tends to be slow. For this reason, it is not apparent which urban forms offers greater accessibility: those with spread-out land uses and more rapid travel, or more compact arrangements in which travel is slower. There are good theoretical reasons to expect that surface travel speeds are all-important in determining accessibility outcomes and that anything that interferes with surface travel speeds, including denser metropolitan development, might degrade accessibility.
Empirical results presented here suggest the opposite: more compact metropolitan regions offer greater auto accessibility even if their travel speeds are somewhat slower. In other words, the proximity effect of density dominates any associated degradation in travel speeds. This suggests that reform of policies that spur low-density, auto-oriented development can yield transportation benefits in terms of increased metropolitan accessibility.
The report also develops indicators for assessing the equity of the distribution of accessibility between individuals within a region. Indicators developed here capture accessibility distributions across dimensions of income, race, and car ownership. Even with a given accessibility distribution by auto and by transit, the equity of the accessibility distribution also depends on the location of carless households within a metropolitan region; indicators also are developed to capture this effect.
Conclusions:
The study suggests several implications for transportation and environmental planning practice. It demonstrates the feasibility of accessibility indicators in intermetropolitan comparison. Transportation outcomes are regularly evaluated between regions; putting accessibility within this intermetropolitan framework can assist in the transfer of accessibility metrics to professional practice. The metrics extend both to the measurement of accessibility overall and to the analysis of the equity of its distribution. The diffusion of accessibility metrics in transportation planning practice will be greatly assisted by the standardization (and standardized reporting) of data on the part of metropolitan planning organizations, particularly the outputs of metropolitan travel models.
Implications of a shift from mobility to accessibility-based transportation practice are far reaching. Currently, land use regulations are frequently deployed to lower development densities, often in an attempt to forestall roadway congestion. This practice, informed by mobility-based transportation thinking, has the effect of reducing the population that is able to live in or otherwise use high-accessibility zones. Results presented here suggest that such practice can degrade accessibility for the population overall; paradoxically, a policy implemented ostensibly to improve transportation outcomes will have degraded accessibility. By contrast, an accessibility-based transportation and land use planning practice would simultaneously create high-accessibility areas (both by auto and transit modes) and facilitate their use by significant shares of the population.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
| Other project views: | All 20 publications | 3 publications in selected types | All 3 journal articles |
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Grengs J, Levine J, Shen Q, Shen QY. Intermetropolitan comparison of transportation accessibility: sorting out mobility and proximity in San Francisco and Washington, D.C. Journal of Planning Education and Research 2010;29(4):427-443. |
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Levine J, Grengs J, Shen Q, Shen Q. Does Accessibility Require Density or Speed? Journal of the American Planning Association 2012;78(2):157-172. |
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Levine J. Is Bus Versus Rail Investment a Zero-Sum Game? Journal of the American Planning Association 2013;79(1):5-15. |
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Supplemental Keywords:
transportation, land use, evaluationRelevant Websites:
http://www.umich.edu/~umaccess/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.