This overview categorizes the commonalities, differences, and gaps across the three pieces, and uses these findings to identify opportunities for future work to advance accessibility practice. We begin with the overall view of the authors on the central importance of a focus on accessibility and the lack of attention by policymakers and practitioners. The second section discusses the formidable challenges the authors agree are involved in moving the concept of accessibility from theory to practice. The third section highlights differing concerns among the authors, and the fourth identifies issues that will require more attention in subsequent work. Finally, the paper presents implications for future applied research and approaches to better engage with the various stakeholders.

Over the course of the 20th century, transportation professionals considered maximizing speed a fundamental pursuit of transportation plans, policies, and practices. This “traffic-based” view led to investments that better connected communities, inspired new technologies within vehicles, and improved infrastructure quality, especially where congestion existed. In turn, a focus on “mobility” began to emerge for moving as many people as efficiently as possible. However, this view focused too narrowly on transportation performance, in the process ignoring the underlying considerations of who takes trips, to where, and how they choose to travel. Accessibility expands on this view.

The underlying goal of any regional transportation system is to connect people to economic opportunity, and accessibility is the umbrella concept to measure the ease of reaching a destination, whether it is a park in one’s neighborhood or a job 20 miles away. Accessibility requires an integrated view of transportation and land use, since decisions made under each policy discipline will intrinsically affect the other. The accessibility concept is also flexible. It can integrate demographic and financial considerations—such as household income or pricing, for example—alongside traditional transportation outputs like travel time to enable a better understanding of how broader economic and social outcomes relate to local transportation design.

Such objective-driven thinking has generated deep support for accessibility theory among academics and practitioners, and a number of developed and developing cities and countries have begun to formally implement accessibility policies into their transportation, land use, and fiscal frameworks. There is now an emerging volume of knowledge and precedent about how an accessibility approach to transportation planning, investment, and operation can improve economic and social outcomes across urban areas.

However, the concept in some ways struggles due to its contextual flexibility. Accessibility can be used as a strict definition of infrastructure quality—like distances to a major highway or transit stop—or as an expansive classification of how well neighborhoods connect to one another. Accessibility can serve a sociological role, helping to explain people’s travel behavior. Accessibility measures can even be used to prescribe new policy solutions related to transportation, land use, and financial needs.

This kind of contextual variability can be seen through the global regions deploying accessibility concepts within their formal transport planning and assessment processes. In the case of the United Kingdom, officials used the objective of reducing social exclusion to incorporate standardized core and local indicators of accessibility. This extensive process created greater coordination between different public agencies, although it failed to move most decision making out of transportation departments. In the United States, national and local governments tend to promote ad hoc accessibility goals without formal regulations tied to specific measures. Meanwhile, some Global South cities now use accessibility policies to better connect their residents to opportunity. Overall though, minimal application is still the norm in most metro areas.

Throughout this paper we make two basic recommendations. The first is to put accessibility more squarely at the center of the study of urban development. The second is to focus urban policymaking more directly on specific problems, such as congestion, pollution, and traffic fatalities. Though there is certainly a need for better knowledge and practice, we argue for a modest change of course, rather than a radical shift in how cities are studied and managed. The externalities associated with transportation and urban development are subtle and interact with each other through many feedback mechanisms. Doing nothing to improve urban accessibility is not a desirable option, but doing something is hard. Nevertheless, we are hopeful that a better balance for research and a better balance for policy practice will bring urban research and practice closer together.

Our examination of the importance of accessibility, and understanding of it, and the measurement challenges proceeds as follows.  Urban accessibility matters. In the United States, Latin America, and Europe, urban residents dedicate nearly half of their spending to housing and transportation. They also dedicate a substantial proportion of their waking hours to travel, particularly in large cities like New York and Mexico City. But while the general finding that households spend a large portion of income on housing and transportation holds in most places, including many poor parts of the world, aggregate figures hide considerable heterogeneity and systematic differences by age, gender, and city size in time spent traveling. In poorer cities, for example, the poorest households sometimes spend substantially less on housing and transportation, but they often do so by consuming extremely little housing and living on lands with uncertain legal title that are also vulnerable to natural disasters like flooding or mudslides. These poor residents are willing to pay an extremely high non-monetary price for accessibility.

URBAN DEVELOPMENT AND URBAN TRAVEL: THE MODELS MEET THE REAL WORLD

The trade-off between housing and transportation costs is central to the earliest models of urban form in idealized cities and to the most recent integrated transportation and land use models of actual cities. Although both types of models provide useful frameworks for understanding development patterns and the potential effects of land use and transportation policies, there are numerous challenges to incorporating real-world complexities into these modeling frameworks. In particular, it is difficult to model accurately the simultaneous location of firms and households, the relative importance of different types of land uses in firm and household decisions, the variety of transportation options, the heterogeneity in firm and household preferences, the role of land use regulation, the effect of new infrastructure, or the legacy of older infrastructure and building forms. There may also be differences between developed and developing cities that vary in nature and not only in degree. Each additional element of real-world complexity adds more nuance to the models but obscures the nature of the trade-offs between transportation costs, housing, and other land uses.

In today’s urbanizing world, facilitating intra-city travel deserves priority because it affects factor productivity, employment, livability, and overall welfare. Achieving the desirably inclusive level of urban accessibility—defined as the ability of a local transportation system to connect people with key destinations—calls for a coordinated approach to planning and implementing land use, managing demand, and building multimodal transport infrastructure.

Developed and developing countries have been struggling to improve urban access. The former are challenged by the need to replace and upgrade legacy infrastructure, modify entrenched land use patterns, and accommodate the needs of aging populations. The latter need to come to grips with rapid and frequently chaotic urbanization that is running far ahead of developmental capabilities. Perhaps most notably, though, both need to employ novel solutions for mobilizing financing and arranging the funding for infrastructure in order to close existing gaps and to accommodate the growth in demand.

In short, cities need to better respond to urban access concerns, and funding and finance play a key role. The way urban leaders finance and fund transportation services is a major determinant of how well residents can connect to economic opportunities.

Urban transport infrastructure tends to be “lumpy” in its ownership and financing. Much of it is financed by transfers, grants, and low-interest loans from the central government. How much tends to vary from place to place, but, for most growing cities, it is never enough. Fiscal arrangements between cities and higher-level governments assign certain expenditure responsibilities to municipalities along with revenue. As the taxes (property, income, sales), fees, and charges assigned to municipal governments rarely generate enough revenue, municipal governments have sought to capture some of the value created by infrastructure spending through a variety of impact and betterment fees.

Some of the larger, better-managed cities with broader economic bases supplement fiscal resources through borrowing from banks and by floating bonds—generally with the approval of the central government. As this too does not always cover the shortfall, cities seek financing from the private sector and enter into a variety of public-private partnerships (PPPs). These have become increasingly popular, as growth of fiscal resources has stagnated while demand for urban access has continued its upward ascent. PPPs, especially for long-lived transport projects, can be problematic, and renegotiation is not uncommon. Nevertheless, cities in all countries are persevering. Once they learn the ropes of bidding, monitoring, regulating, and pricing, some of the difficulties are likely to ease.

Needless to say, improving urban access calls for effective governance. Good leadership—combined with improving governance structures and meritocratic staffing—certainly helps, but achieving and sustaining good governance in the vertical and horizontal domains can be a considerable undertaking for countries at all levels of development. While governance will remain a priority, it is unclear that mediocre albeit adequate governance necessarily holds back the economic performance of cities so long as they can muster the private entrepreneurial energies and the private sector can finance investment in productive assets.