From mobility to accessibility by proximity: an Inclusive Accessibility by Proximity Index (IAPI)

Several cities worldwide are committed to reducing the intensities and impacts of people's car-based travels and promoting more sustainable and inclusive urban environments by providing accessible services and opportunities in physical proximity and favoring active mobility. Such an attempt is oriented by a positive vision of post-car mobility based on the concept of "accessibility by proximity," where a focus on proximity induces a shift privileging accessibility - and its contribution to social inclusion - over mobility, thus prioritizing the possibility that each person accesses basic needed opportunities (physical proximity) while reinforcing social local ties (relational proximity). Implementations of the principle of accessibility by proximity, such as the 15-minute city, have recently gained interest as a reacrion to current crises: on the one hand, planning for accessibility by proximity is an attempt to reduce the social, spatial, and environmental effects of forms of hypermobility induced by massive motorization and urbanization which are directly connected to the climate crisis. The scale to which post-car city measures apply represents a lever for providing local actions to respond to global challenges and create more sustainable living.
On the other hand, the Covid-19 pandemic has highlighted the relevance of proximity and accessibility between people and their needed services as indispensable conditions for ensuring high quality of urban life. Still, the pandemic has shown how accessibility conditions for different population groups are highly uneven and related to individual and contextual factors contributing to the (re)generation of profound social and spatial inequalities. Thus, planning for accessibility by proximity can help cities understand the role that specific transport infrastructures and basic services play in the economic and social life of the territory and how accessible these services are for different population groups, preparing cities to orient their development and spatial distribution according to equity principles and sustainability goals. Implementing in concrete terms the accessibility by proximity concept raises several operational challenges such as the need for reliable analytical tools to measure current inequalities in spatial accessibility via active mobility for different groups of road users, including the most vulnerable. Based on this background, the paper introduces an Inclusive Accessibility by Proximity Index (IAPI), a scalable and context-sensitive GIS-based tool for assessing accessibility levels to daily activities deemed essential for a city's inhabitants while recognizing the impact that the physical and perceptual characteristics of urban spaces play in favoring active mobility modes and fostering physical and relational proximities. By collecting and employing objective and subjective data about the responses of different mobility profiles (pedestrians, cyclists, people with reduced mobility) to the spaces and paths they live and cross daily, the IAPI can support the design of planning and urban design measures aimed at promoting walkability and cyclability and improving accessibility via active modes to daily services, thus envisioning a more sustainable and inclusive city. Based on the experience conducted in the testbed of Bologna (Italy), the paper describes the IAPI methodology and its empirical application outlining the possible contribution of the index in supporting welfare and urban design policies.