VISUALIZING ACCESSIBILITY: AN INTERACTIVE TOOL AND AN APPLICATION TO AN EMPIRICAL STUDY OF URBAN DEVELOPMENT AND PUBLIC ENGAGEMENT
Pierluigi Coppola, University of Rome, Tor Vergata, Stefano Pensa, SITI, Matteo Tabasso, SITI
This paper presents an accessibility interactive visualization tool, and the application to an empirical study aiming at exploring its potential usability to engage public stakeholders into the assessment of different options of urban development.
While there is a large body of literature focusing on the theoretical definitions and measures of accessibility, the extent to which such measures are applied into practice to assess project alternatives is less frequent. To increase usability of accessibility instruments, visualization tools are commonly recognized as the most effective methodology, particularly in those processes involving public stakeholders and non-experts.
This paper presents an accessibility Interactive Visualization Tool, named InViTo (Pensa et al., 2013), and its application to an empirical study (i.e. Rome) aiming at exploring the potential usability of the tool in engaging public stakeholders into the assessment of different urban development options (e.g. modifying land-uses, new infrastructures, etc.).
InViTo is a platform, based on free and open technologies such as Google Maps and Google Fusion Tables, showing real-time outcomes of accessibility levels for the cells (i.e. zones, areas, blocks, …) of an urban grid, with respect to “urban items” related both to transport infrastructures (such as underground and railway stations, motorways junctions, parking facilities, etc…) and to urban facilities (such as green and pedestrian areas; school and universities; hospital; shopping malls, etc...). Accessibility is here defined as the perceived utility (by urban agents, e.g. individuals, households, business owners,…) of residing in a given area, depending on the proximity to the selected urban items. For a given cell, accessibility is computed by summing up the utilities (or dis-utilities) related to all the selected items (each located at given distances). InViTo enables to assign specific weights for each item, according to multi-criteria methods.
The tool requires geo referenced data for each item on an interactive map of the study area. It requires also estimation of the curves of perceived utility as a function of the distance from each of the considered items. To this aim, disaggregate SP-surveys need to be carried on, asking residents of the study area to rank the levels of utility (in a Likert scale from -7 to +7) of several urban items located at pre-defined intervals of distance (e.g. 100-250 meters, 250-500 m, …). The curves represent the perceived utility as a function of distance, and allow to analyzing the relative importance of items as well as the utility trends with respect to distance. For example, the utility of residing in a given area results to be decreasing with distance from underground stations or from green areas, whereas it increases with distance for items like motorway junctions, railway tracks, etc., that typically spoil the urban environment due to noise and pollutant emissions, visual intrusion and so on.
The results of the application to the empirical case study of Rome allowed to validating the approach and producing accessibility maps of future urban development options, easy to be managed and understood also by non-expert end-users. These were presented during a workshop with practitioners and local stakeholders, yielding new insights to the undergoing debate on usability of accessibility instruments and public engagement.
Association for European Transport