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.
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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, but minimal application is still the norm in most metro areas.
Encouraging more global cities and regions to adopt accessibility practices will require addressing a series of major constraints and barriers. Shifting political interests can lead to inconsistent support for accessibility policies, while governance structures often dissuade the kind of cross-agency collaboration critical to advancing accessibility goals. Conceptually, governments and their civic peers still struggle with connecting transportation decision making to broader regional objectives, whether these objectives concern equity issues, land development, or financial sustainability. Additional exploration of accessibility pricing and its impact on equity is another area of need. However, several emerging approaches show promise in implementing accessibility practices worldwide, including the availability of open data and software, community engagement tools, and new modeling approaches.
