A New Measure of Accessibility based on Perceived Opportunities

Accessibility is a key concept in describing and simulating the interactions between activities and transportation in any given area. Over the decades several definitions and related indicators have been proposed for accessibility including opportunity- based and utility-based, active and passive, descriptive and behavioral ones. Limitations of the various definitions and related indicators have been discussed in the literature on the basis of their lack of behavioral content and/or lack of clear physical meaning and/or the lack of sound statistical procedures to estimate the parameters involved. In this paper a new behavioral definition of accessibility, both active and passive, is proposed and tested, based on the number of opportunities perceived by an (average) individual for satisfying his/her needs in the study area. These general definition overcomes most shortcomings of previous definitions belonging to the same class such as isochrones-based measures which, in turn, can be cast as particular cases of perceived opportunities measures.