Developing a Common Narrative on Urban Accessibility: an Urban Planning Perspective

Developing a Common Narrative on Urban Accessibility: An Urban Planning Perspective Gilles Duranton1 & Erick Guerra November 2016 Table of Contents Executive summary .....................................................3 4.1 Defining accessibility .............................................18 1. Introduction ..............................................................5 4.2 Measuring accessibility .........................................19 2. Transportation and housing context .......................7 4.3 Accessibility, travel behavior, and urban form ....21 3. Setting the scene: urban development and urban 4.4 Transportation supply and accessibility ...............22 travel .............................................................................9 5. Some policy challenges and implications .............23 3.1 A simple framework (or perhaps already not so simple) ..........................................................................9 5.1 Challenges to adopting accessibility ....................23 3.2 Firms also decide where to locate ........................10 5.2 Providing appropriate space for transportation ..24 3.3 Another complication: Urban resident and firms are 5.3 Investing in transit .................................................25 different ........................................................................11 5.4 Measuring the transportation impacts of new 3.4 Adding realism: Travel is not only to work ...........12 development ................................................................26 3.5 Adding realism: the transportation system .........12 5.5 Spatial mismatch / jobs-housing imbalance .......26 3.6 Adding realism: land use is heavily regulated ....14 5.6 Dealing with congestion: the ideal and feasible .28 3.7 Urban structures last forever ................................15 6. Conclusion ................................................................29 3.8 Thinking about developing cities requires adding References ....................................................................31 even more moving parts .............................................15 Endnotes .......................................................................36 4. Defining and measuring accessibility in an urban setting ...........................................................................18 Developing a Common Narrative on Urban Accessibility: 3 An Urban Planning Perspective Executive summary Drawing on examples from poor, rich, and middle- understanding of it, and the measurement challenges income cities, this paper examines the importance, proceeds as follows. theoretical understanding, and empirical measurement of urban accessibility. We argue that accessibility is The time, cost, and effort of urban the main quantity to consider from an urban resource transportation and housing allocation standpoint, since it links land use and Urban accessibility matters. In the United States, Latin transportation, the two primary urban consumption America, and Europe, urban residents dedicate nearly goods. But despite the importance of accessibility, half of their spending to housing and transportation. a sparsity of empirical knowledge and a disconnect They also dedicate a substantial proportion of their between policymaking and accessibility outcomes waking hours to travel, particularly in large cities have led many researchers to retreat into narrow like New York and Mexico City. But while the general areas of expertise—such as land use, housing, or finding that households spend a large portion of transportation treated in isolation—and many urban income on housing and transportation holds in most policymakers to ignore accessibility altogether. Even places, including many poor parts of the world, when data are good, the politics of land use and aggregate figures hide considerable heterogeneity and transportation decisions rarely favor accessibility as an systematic differences by age, gender, and city size in important policy outcome. As a result, urban policies time spent traveling. In poorer cities, for example, the often fail to allocate land use or transportation either poorest households sometimes spend substantially efficiently or equitably. less on housing and transportation, but they often do so by consuming extremely little housing and living on Throughout this paper we make two basic lands with uncertain legal title that are also vulnerable recommendations. The first is to put accessibility to natural disasters like flooding or mudslides. These more squarely at the center of the study of urban poor residents are willing to pay an extremely high development. The second is to focus urban non-monetary price for accessibility. policymaking more directly on specific problems, such as congestion, pollution, and traffic fatalities. Urban development and urban travel: the Though there is certainly a need for better knowledge models meet the real world and practice, we argue for a modest change of The trade-off between housing and transportation course, rather than a radical shift in how cities are costs is central to the earliest models of urban studied and managed. The externalities associated form in idealized cities and to the most recent with transportation and urban development are integrated transportation and land use models of subtle and interact with each other through many actual cities. Although both types of models provide feedback mechanisms. Doing nothing to improve useful frameworks for understanding development urban accessibility is not a desirable option, but doing patterns and the potential effects of land use and something is hard. Nevertheless, we are hopeful that transportation policies, there are numerous challenges a better balance for research and a better balance for to incorporating real-world complexities into these policy practice will bring urban research and practice modeling frameworks. In particular, it is difficult to closer together. model accurately the simultaneous location of firms Our examination of the importance of accessibility, and and households, the relative importance of different types of land uses in firm and household decisions, Developing a Common Narrative on Urban Accessibility: 4 An Urban Planning Perspective the variety of transportation options, the heterogeneity Policy challenges and implications in firm and household preferences, the role of land Partially as a result of the challenges with the concept, use regulation, the effect of new infrastructure, or accessibility plays little role in day-to-day investment the legacy of older infrastructure and building forms. or policy decisions. The complexity of defining and There may also be differences between developed measuring accessibility makes it a difficult metric for and developing cities that vary in nature and not assessing policy and makes it somewhat abstract only in degree. Each additional element of real- and hardly pressing. Voters and policymakers have world complexity adds more nuance to the models a much more personal connection to whether they but obscures the nature of the trade-offs between have an easy time finding parking, whether housing is transportation costs, housing, and other land uses. too expensive, and whether the trains come on time. Furthermore, different pieces of the accessibility puzzle Efforts to measure accessibility resonate differently with different groups of people Using this framework, measuring accessibility—which and individuals. While it is tempting to suggest that we define simply as the ease of reaching destinations— planning for accessibility requires a holistic approach becomes conceptually as well as empirically that can accommodate this conceptual and empirical challenging. At its simplest, a labor market measure complexity, a holistic approach would likely backfire of accessibility might count the total number of jobs since it is difficult, perhaps impossible, to decide accessible to a place or person within a fixed time and on an optimal accessibility level, let alone measure by a fixed mode under typical travel conditions. More it. Instead, by looking at the examples of providing complicated measures weigh accessibility indices appropriate space for transportation, investing in by job type, time of day, and distance. However, transit, evaluating the transportation impacts of at its heart, accessibility is an individual concept. new land uses, providing affordable housing, and To take an extreme example, proximity to a butcher dealing with congestion, we argue that policymakers shop does not factor into accessibility for vegetarian should consider whether policies, plans, investments, households. It is also a relative concept. People rarely and regulations will tend to increase or decrease go to the closest restaurant, attend the closest religious accessibility at the margin. institution, or work at the closest job. While ad hoc measures of accessibility such as walk scores are fast becoming more available and may be informative, they still constitute deeply unsatisfactory measures. Yet more theoretically and empirically robust measures that incorporate multiple trip purposes, travel modes, and user preferences are still out of reach and unlikely to be commonly used anytime soon. Because accessibility is a hard concept that is often poorly understood and always poorly measured, it is an obvious obstacle to sound urban development policies. As a result, different people mean different things when they talk about accessibility and end up talking past

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