Accessibility and Mobility

Conceptual Discussion

From common spoken language to newspaper articles and even to papers of a more scientific nature, accessibility and mobility are commonly used indiscriminately and even as synonymous. Moreover, one can say that in recent years accessibility has even become a trendy concept in both social and political contexts, with accessibility often preferred over mobility independent of the concept being referred to at the moment. In fact, the term accessibility has become very common, being one of those terms almost everyone uses (especially in planning and politics) although clear notions of its meaning or of how to measure it are far less common.

Even though both concepts translate a specific ability related to spatial (or virtual) connectivity, they refer to different, although interconnected, abilities. Looking at plain definitions in common dictionaries, we find the word mobility to be the ability to move and the word accessibility to be the ability to access or reach. In other words, mobility represents the ease of movement while accessibility represents the ease of reaching desired destinations (opportunities or activities).

The concept of mobility can easily be operationalized through a number of common indicators measuring if, how, and how much travel is performed. Most common indicators measure travel distance, time, frequency (number of personal or freight trips), and mode choice. In contrast, accessibility is a far more ambiguous notion, implying a range of aspects, such as the distribution of potential destinations; the magnitude, quality, and character of activities; the performance of the transportation system; the characteristics of the individuals; and the times at which the individuals are able to participate in activities, among others. Conceptual discussion around accessibility has been somewhat limited. The multidimensional nature of accessibility justifies why several researchers in this field have advocated that the definition of the concept of accessibility depends on the objective for which it is intended. Most common accessibility measures identify areas in equidistance/time of important destinations such as capital cities, city centers, or major transport nodes (isochrones), catchment areas or market areas of important public services or transport nodes, and number or diversity of activities accessible or utility of that access. For more detail on measures and indicators of accessibility and mobility, see below.

Mobility represents the choices people make, while accessibility represents the choices people have, of which only some will actually be made. In this sense accessibility can be regarded as potential for mobility (in short, potential mobility). In fact, mobility or actual travel behavior is an indicator of accessibility but is not a measure of it; that is, high mobility might be an indication of high accessibility, but it is not possible to measure accessibility based on the amount or form of travel.

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