From Mobility to Accessibility: Transforming Urban Transportation and Land-Use Planning

FROM MOBILITY TO ACCESSIBILITY

Transforming Urban Transportation and Land-Use Planning

Jonathan Levine

Joe Grengs

Louis A. Merlin

CORNELL UNIVERSITY PRESS    ITHACA AND LONDON

Dedicated in loving memory

Rose Aronowitz Levine

Hillel Benjamin Levine

Judith Langer Merlin

Contents

Acknowledgments

List of Abbreviations

Introduction: The Accessibility Shift

1. What Is Transportation For?

2. Evolution of the Accessibility Concept

3. Accessibility in Everyday Planning

4. Accessibility and Urban Form

5. The Special Case of Public-Transport Accessibility

6. Accessibility in Social-Equity Evaluation

7. Nonwork Accessibility

Conclusion: Envisioning the Accessibility Shift

Appendix A: Procedure for Accessibility Analysis for Land-Use Projects

Appendix B: Variables Used in the Text

Notes

Bibliography

Index

Acknowledgments

We are grateful to the many individuals and organizations that helped make this book possible. Indispensable institutional support came from the Rockefeller Foundation Bellagio Center, the Environmental Protection Agency, the Graham Sustainability Institute, the Dow Sustainability Postdoctoral Fellowship, the Federal Highway Administration, the NEXTRANS Center, and the Taubman College of Architecture and Urban Planning at the University of Michigan. Data were generously contributed by the City of Ann Arbor, the Accessibility Observatory at the University of Minnesota, the Southeast Michigan Council of Governments, the Alamo Area Metropolitan Planning Organization, and dozens of other MPOs around the United States.

Research findings in chapter 3 were previously published in Jonathan Levine, Louis Merlin, and Joe Grengs, Project-Level Accessibility Analysis for Land-Use Planning, Transport Policy 53 (2017): 107–19, and in Louis A. Merlin, Jonathan Levine, and Joe Grengs, Accessibility Analysis for Transportation Projects and Plans, Transport Policy 69 (2018): 35–48. Research findings in chapter 4 were previously published in Jonathan Levine, Joe Grengs, Qingyun Shen, and Qing Shen, Does Accessibility Require Density or Speed?: A Comparison of Fast versus Close in Getting Where You Want to Go in U.S. Metropolitan Regions, Journal of the American Planning Association 78, no. 2 (2012): 157–72. All used by permission.

Qing Shen and Qingyun Shen were our partners in much of the research reported in chapters 4 and 7, and Qingyun provided brilliant assistance throughout much of the empirical research of the book. We benefited from superb research assistance as well from Matan Singer, Alexandra Markiewicz, Doug Koloszvari, Jason Enos, Patrick Dieter, Arthur Prokosch, Wenting Chen, and Chao Liu. Zachary Graham, from the Alamo Area Metropolitan Planning Organization, provided assistance with data and modeling. Guillaume Barreau programmed a website to render methods in chapter 3 accessible to planners in practice. Prashanth Raju enhanced the consistency and clarity of the graphics. Two anonymous reviewers and our editor, Michael McGandy, offered constructive feedback that greatly improved the draft. Julie Steiff similarly improved the text with her professional editing, and we benefited from comments on previous drafts from colleagues, students, and family including Jacob Yan, Matan Singer, Adam Levine, Rob Goodspeed, Adam Millard-Ball, Deena Levine, and Michael Lipsett.

Finally, our gratitude goes to Noga Morag-Levine, Suzanne Copsey, and Ki-Wing Merlin for their loving support throughout the process of creating this book.

Abbreviations

BRT Bus Rapid Transit

CEQA California Environmental Quality Act

EIR Environmental Impact Report

EJ Environmental Justice

FHWA Federal Highway Administration

FTA Federal Transit Administration

GTFS General Transit Feed Specification

LOS Level of Service

LRT Light Rail Transit

MAP-21 Moving Ahead for Progress in the 21st Century Act

MPO Metropolitan Planning Organization

MRCOG Mid-Region Council of Governments

MSA Metropolitan Statistical Area

NAICS North American Industry Classification System

NEPA National Environmental Policy Act

NHTS National Household Travel Survey

NMDOT New Mexico Department of Transportation

NTD National Transit Database

SMART System Management and Allocation of Resources for Transportation

TAZ Traffic Analysis Zone

TIGER Transportation Investment Generating Economic Recovery

TIP Transportation Improvement Plan

VKT Vehicle-Kilometers Traveled

VRM Vehicle Revenue Miles

Introduction

THE ACCESSIBILITY SHIFT

Imagine that you have a list of tasks to accomplish that requires you to travel to a number of destinations today: work, shopping, day care, and maybe a restaurant or cinema. Unlike a typical day, today you have the freedom to choose between two metropolitan areas to meet these ordinary needs. While both regions host the full range of destinations, the first region boasts more rapid surface travel—less congestion, faster highways, and more rapid transit—than the second. The second has slower travel, but your destinations are closer to your starting point and to one another, such that you can accomplish your task list with less investment of time and money. Based solely on your ability to travel quickly, region number one would seem to be the better choice. But knowledge about travel speeds would not give you a complete picture of your ability to meet your needs in that region; the relative locations of your destinations would matter as well. If you choose the second region because its closer destinations more than offset the slower travel it supports, you are selecting the higher-accessibility option.

Ironically, you are choosing the region that current transportation-planning methods identify as problematic.¹ Since the mid-twentieth century, transportation outcomes, together with the transportation dimension of land use, have largely been planned and evaluated within a framework based not in accessibility, but in mobility. Faster movement, particularly by cars, is treated as the central goal, without attention to accessibility as an outcome. In this book we advocate a shift from mobility to accessibility as the basis for transportation and land-use planning, arguing that such a shift (a) is compelled by the very purpose of transportation; (b) would be transformative to the practices of both transportation planning and land-use planning; but (c) is impeded by numerous misconceptions. The misconceptions constitute impediments to the mobility-to-accessibility shift, termed here the accessibility shift, impediments we seek to help overcome.

Accessibility and Mobility

The concepts of accessibility and mobility are readily distinguished by considering what would count as an improvement in each.² An improvement in mobility is an increase in the territory that can be reached for a given investment of time and money, while an improvement in accessibility is an increase in the destinations that can be reached for a given investment of time and money. To be more precise, destinations vary in their value; most people would appreciate access to a supermarket more than to a convenience store, for example. So an accessibility improvement is more precisely defined as an increase in the value of destinations that can be reached for a given investment of time and money. Physical accessibility, the focus of this book, refers to the potential for traveling to actual destinations, but the concept can be broadened to accessibility more generally by including remote electronic interaction with virtual destinations and delivery of goods and services to one’s location. While physical accessibility varies widely by travel mode, it is equally relevant to auto drivers, public-transport riders, pedestrians, and cyclists; it is the principal service that people seek from transportation regardless of the means they choose. And though improving accessibility may help further planning goals including social equity, environmental performance, and multimodalism—and may be motivated in part by the struggle to achieve them—accessibility is not equivalent to those goals. Accessibility has, in some cases, become a shorthand for a long wish list of desirable transportation outcomes; we reject this expansive view in favor of the more limited, and more workable, definition given here.

Reliance on mobility as a guiding planning principle is evidenced in current policy and in the physical form of the built environment in metropolitan areas in the United States and many other countries around the world. When evaluating the performance of a transportation system, the fundamental criterion for success has long been faster vehicle-operating speed.³ Common indicators of this include delay per capita, dollars wasted while waiting in traffic, and highway level-of-service.⁴ These mobility metrics are not simply after-the-fact assessments but are also used proactively to guide policy toward transportation investment and land-use regulation.⁵ On the ground, this often translates into a singular focus on fast and wide highways and land-use regulations that strive to forestall traffic congestion by limiting allowable development heights or densities, a combination of policies that can increase metropolitan travel distances by inducing an increasing spread of origins and destinations.⁶

This focus on mobility stands in contrast to a cornerstone of modern transportation planning: the notion that the demand for transportation is largely derived from the demand to reach destinations.⁷ Economists refer to a derived demand as a demand for an intermediate good or service that occurs as a result of the demand for a final good or service. Examples include fertilizer purchased by farmers in order to grow crops or electrical power consumed in order to attain desired services such as illumination or computing power. Evaluating farmers’ productivity with metrics of fertilizer consumption rather than crop production would be an obvious error that, if used to guide decision making, would surely lead to bad policy. Transportation planning is largely built on a similar error, because the derived-demand view, a consensus across the transportation professions, implies that mobility is primarily a means in transportation rather than an end.

If the goal that drives current transportation planning—mobility—differs from the service that people seek from transportation—accessibility—the planning process would tend to overprovide the former and underprovide the latter. The transportation and land-use systems would require a high degree of person and vehicle movement to overcome the great distances between origins and destinations. A shift to an accessibility logic would add proximity to the lexicon and tool kit of the transportation planner. Where mobility-based transportation planning has been largely indifferent to the distance between origins and destinations, a shift toward accessibility would seek to create gains for current and future residents through mobility and proximity in combination. Aligning the logic of transportation planning with the core purpose of transportation is about ensuring that people get more of what they want out of the system: access to destinations.

And the observation that transportation demand is derived is in fact a function of people and what they want. Transportation demand is not derived as a matter of definition or axiom; if people were observed to behave as if they were usually seeking movement for its own sake when they travel, the derived-demand conclusion would be unsupported. While some travel is clearly for the sake of movement, the empirical evidence strongly supports the idea that, for a large majority of trips, time spent in travel is a cost that people bear in order to reap the benefits available at their destinations (see chapter 1).

Derived Demand and the Accessibility Shift

The derived nature of most transportation demand (which we will refer to as the derived-demand framework) is not at all controversial. Quite the opposite: this fundamental concept is embedded throughout mainstream transportation-planning methods.⁸ For example, travel-demand models rely on the arrangement of land-use patterns across a region to forecast travel flows; this capacity to forecast travel largely on the basis of the spatial arrangement of origins and destinations is a direct outgrowth of the derived-demand framework.⁹ If transportation were undertaken simply for the purpose of movement, then the ease with which destinations could be reached would not be a useful predictor of trip making in travel-demand models.

Derived demand is also at the core of traditional cost-benefit evaluation methods for transportation planning. Consider, for example, a bypass route that allows travelers to reach their destination more quickly. Cost-benefit analysis considers the travelers’ time savings to be the principal relevant benefit of the infrastructure investment. After the investment, the travelers consume less mobility because they can now take a more direct route to their destination. If movement itself were the service travelers desired, switching to a shorter highway route would represent people’s consuming less of what they want; it would paradoxically be considered a harm rather than a benefit. The derived-demand framework avoids this dilemma by viewing mobility correctly as an intermediate service that is consumed for the sake of reaching one’s destination; in this way derived demand is implicit in all realms in transportation planning and policy.

But while the fields of transportation planning, engineering, and economics are all based on this destination-oriented view of transportation, there is an implication that they have too rarely confronted. If the demand for travel is indeed mostly derived, then assessments of the quality or speed of movement, when performed in isolation, cannot reveal the extent to which people’s transportation needs are being met. Such an assessment would need to change to one based on people’s capacity to reach destinations, a function of both the speed of their travel and destination proximity, not just their ease of movement. In this way, the accessibility shift, a definition of what constitutes success in transportation, is compelled as a matter of logic by the derived nature of transportation demand, which is a matter of empirical human experience.

This accessibility shift would align transportation and land-use planning with thinking in other professions. For example, site selection for retail facilities has for decades been driven by accessibility considerations.¹⁰ The real-estate truism that the components of value are location, location, location is, in large part, an accessibility-related assertion, and measured accessibility has in fact long been a key component of land-value models.¹¹ Real estate agents know that people frequently express appreciation for their home and neighborhood on the basis of the destinations reachable from them; rarely do they express the appreciation based on the travel speeds on the roadways serving their locales. The accessibility shift does not require transportation and land-use planners to convince others to begin to act in an accessibility-aware fashion; it does, however, demand reform of the principles and norms of the profession itself.

Neither does the shift represent new governmental intervention into markets. The practice of transportation and land-use planning, with its massive public investment in transportation infrastructure, detailed and prescriptive regulation of land use through municipal zoning and subdivision controls, and reliance on tools including taxation, eminent domain, and subsidy, is inherently an exercise in governmental intervention into markets.¹² The accessibility shift seeks to align that ubiquitous intervention with transportation’s purpose.

Grounding the accessibility shift in the derived-demand framework contrasts with some traditions in accessibility-related thinking. The primary benefit of the accessibility shift is increasing people’s capacity to reach destinations, yet accessibility is frequently seen first and foremost as a means to yield other, ancillary benefits aligned with current policy imperatives: reductions in vehicle kilometers traveled (VKT) and attendant pollution and greenhouse-gas emissions; improvements in the equity of the transportation and land-use system; increases in active transportation including walking and cycling; containment of metropolitan sprawl; or even reductions in roadway congestion.¹³ All these outcomes are desirable, and many of them may plausibly be aided by a shift from mobility to accessibility as the central framework of transportation and land-use planning. They may even be the prime motivators for many who might seek a shift to accessibility-based planning.

But evidence of accessibility’s ancillary benefits, however welcome, ought not to be the desirability test of, or necessary precondition for, the accessibility shift. To see this, consider the universe of mobility-increasing actions. Some of them will increase accessibility, while others will leave accessibility unchanged or even degrade it. If the purpose of most travel is reaching destinations, the latter two sets of actions fail to further that purpose (and the last undermines it). Hence the derived-demand framework implies rejection of a mobility criterion for transportation success when considered in isolation. By contrast, consider the universe of accessibility-increasing actions. Some will improve mobility, while others will leave it unchanged or even degrade it. All of them, however, would further transportation’s purpose by improving people’s ability to reach destinations. This is sufficient to establish their transportation benefit; any benefits in other realms would be a bonus. In this way, accessibility is much more than one desirable framework, a politically attractive concept, as Ilan Salomon and Patricia Mokhtarian assert, or Gerald Houseman’s handy term to use in discussions of mobility . . . quite popular among . . . environmentally conscious writers.¹⁴ The derived-demand framework implies that accessibility is an inherent benefit apart from any ancillary benefits it might also provide. This idea is the derived-demand rationale for the accessibility shift.¹⁵

The inherent, rather than instrumental, view of the accessibility shift faces a significant obstacle. Concerns about environmental performance, human health, or congestion are institutionalized through government agencies at various levels, nongovernmental organizations, and private-sector mobilization. By contrast, there are few integrated transportation/land-use agencies, or departments of accessibility, that would be well positioned to champion the accessibility shift. For this reason, the temptation to condition the shift on already-institutionalized concerns is great. But that linkage comes at a cost: while evidence of these ancillary gains can add political urgency to the accessibility shift, such conditioning implies that scientific uncertainty regarding accessibility’s purported benefits in areas such as emissions reductions or health improvements—an ever-present feature of large societal questions such as these—would be an argument against the shift. Yet rejecting the accessibility shift does not amount to a neutral default, but rather a reversion to mobility-based planning and evaluation.

The derived-demand rationale may be particularly important given the time scales over which behavioral shifts operate. For example, consider the travel-behavior impacts of developing an individual site in a walkable or transit-friendly fashion when the regional situation for that neighborhood is auto-oriented. Any VKT-reduction effects are likely to be slight because so much of the travel from the neighborhood is to region-wide destinations and will continue to be by car.¹⁶ Policy reform in this realm, however, aspires not merely to islands of walkable urbanism within a sea of sprawl, but to overall transformation in metropolitan-development trends. Hoped-for reductions in driving are thus much greater than those that isolated pockets could ever produce (even on a per-capita basis), yet proof of these greater benefits will always be uncertain in the near term since cities change slowly. Accessibility is the immediate benefit that can be pursued as policy reformers seek the more uncertain payoff of long-run driving reductions based on shifts in patterns of development.

Our primary argument—that the derived-demand framework compels an accessibility perspective and establishes accessibility as the appropriate evaluative framework for transportation planning—has not always been evident. For example, derived demand has been viewed as impeding rather than compelling the accessibility shift. Perhaps a major reason that the analysis of accessibility has not been frequently proposed as a basic component of a social report, is the common notion that movement is a ‘derived’ demand. . . . It could be argued that because transportation and physical accessibility constitute means to achieving ends such as income, health, and education, accessibility need not be singled out as a component of a set of indicators, wrote Martin Wachs and Gordon Kumagai in 1973.¹⁷ In other cases, authors cite the derived-demand watchword but fail to acknowledge its inconsistency with a mobility-based definition of the purposes of transportation, as Jean-Paul Rodrigue wrote in 2009: What are the differences between a Boeing 747, an oil tanker, a car and a bicycle? Extensive indeed, but they each share the common goal of fulfilling a derived transport demand, and they thus all fill the purpose of supporting mobility.¹⁸

Some authors go further, portraying accessibility as a means to mobility rather than the reverse, despite explicit acknowledgment of derived demand. "Unsuccessful solutions to this problem [congestion] and the wide recognition of the effects of accessibility has [sic] resulted in the idea that by improving accessibility, reductions in congestion . . . could be attained. . . . In this approach travel is considered a derived demand, which implies that the decision to travel or not originates from the need to go to a particular destination," wrote Irene Casas in 2003.¹⁹

A Distinct Relationship between Accessibility and Mobility

Traditionally, transportation planning and engineering have defined themselves in mobility terms; transportation investments or policy interventions including highway-capacity expansion, public-transport deployment, and even land-use planning are evaluated in terms of their capacity to promote mobility, which is often interpreted as prevention or alleviation of highway congestion.²⁰ This focus on mobility needs to be altered in light of the derived-demand framework. Mobility would become one means to achieve accessibility; other possible pathways would be proximity and connectivity (figure I.1). Connectivity here refers to the delivery of goods and services to one’s location, whether virtually (e.g., internet downloads) or physically (e.g., package delivery, traditional utilities). But mobility and proximity exist in tension with each other. Compact places with many origins and destinations near one another tend to be locations where surface transportation is slow; conversely, areas of rapid surface travel tend to be low-density areas where origins and destinations are more dispersed.

FIGURE I.1 Relationships among mobility, proximity, connectivity, and accessibility in a revised hierarchy of transportation goals

The relationship between mobility and accessibility runs through urban form, or the patterns of origins and destinations across a region. It is not obvious by definition which urban forms offer higher accessibility: areas of rapid surface travel and low proximity, or areas offering high proximity of origins and destinations but slower travel. The accessibility impacts of moving from an area with slow travel and nearby destinations to one with faster travel and spread-out land uses would be a function of the net effect of speed and distance change between the regions. For example, if the region with widely spread origins and destinations had travel speeds for a given mode that more than made up for its great distances, it would be the higher-accessibility region of the two. For this reason, as an evaluative framework, accessibility does not inherently favor any particular urban form, but rather seeks transportation and land-use systems that support people’s ability to meet their needs through interaction with their destinations.

Improved mobility does not guarantee improved accessibility and can even be associated with degraded accessibility over the long term because of land-use change. For this reason, current evaluations of transportation outcomes based in mobility alone suffer from a distinct logical flaw. If the purpose of transportation is not movement but access, then a mobility improvement that is associated with degraded accessibility would leave people with less time and money with which to interact with their destinations, and for that reason could not be viewed as a transportation-system improvement. While actual impacts would be a matter for empirical assessment (see chapter 4), the possibility of mobility improvements that fail to improve, or even degrade, accessibility argue for a reform of the definition of transportation success.

Accessibility as Potential for Interaction

Accessibility is an intangible potential for interaction as opposed to concrete revealed travel behavior. It may be difficult to believe that improvements in the potential for interaction that do not materialize as changes in trip making can be a meaningful indicator of anything, least of all the quality of a transportation system, but accessibility, rather than revealed travel behavior, is the meaningful indicator of these benefits. Consider, for example, average commuting time—a measure of revealed travel behavior, rather than accessibility—as a candidate indicator. A low average commuting time might or might not indicate great benefits from a location, since vastly different areas will demonstrate similar values; for example, at 18.9 minutes, downtown Washington, DC, and rural Burdett, Kansas (population 247), have identical average commute times.²¹ These short average times are the products of a concentration of nearby job locations in the former case, and an absence of commuting opportunities in the latter; transportation-system benefits accruing to the two would not be remotely comparable. Another example is