Measuring Inclusive Accessibility by Proximity

EX-TRA is experimenting with an Inclusive Accessibility by Proximity Index (IAPI) to support safe and inclusive active mobility at the neighbourhood scale.


The IAPI - conceived by Politecnico di Milano (Polimi) in collaboration with the Technical University of Munich (TUM) - is a quantitative tool to measure access levels to urban opportunities and basic services through active mobility. Consequently, it can be applied to orient actions for improving accessibility to essential daily services at the neighbourhood scale. Within a theoretical framework that recognises accessibility as a necessary condition to guarantee “activity participation” and social inclusion, the IAPI has been developed to measure the level of basic accessibility, here defined as the ability of the transport system to provide all persons with a sufficient level of accessibility to allow everyone to participate to a set of enabling and valued activities and opportunities (Martens 2017).

Critically assuming time as a parameter to measure access to urban services and opportunities as proposed in recent experiences - such as the Ville du quart d’heure in Paris - IAPI refers to three main conditions affecting the ability to access the daily opportunities: accessibility for three mobility profiles such as pedestrians, cyclists, people with reduced mobility (accessibility for whom?), accessibility to a set of basic daily services, that are essential for ensuring social inclusion (accessibility to what?), and accessibility by walk and cycling to reach them (accessibility by what means?).


The Index has been tested in Crescenzago, a district in the northeast of Milan, for two reasons. Firstly, it is a peripheral area with heterogeneous morpho-functional conditions and an imbalance in the availability of services. Additionally, accessibility is strongly affected by large monofunctional platforms and infrastructures that act as barriers, particularly for east-west connections (city rail, via Palmanova, the Martesana canal). Secondly, it is of particular interest because the Local Administration will experiment in this area transformation project to support the 15 minutes city.


Crescenzago district (NIL 19) in the North-East part of Milan Ⓒ Politecnico di Milano

Within this framework, the proposal for an Inclusive Accessibility by Proximity Index (IAPI) aims at providing:

  • Quantitative assessment and classification. It represents a quantitative criterion for measuring different access levels by foot and bike to urban opportunities and basic services.

  • Orientation for urban policies and street experiments. It allows identifying disadvantaged areas in access to basic services and opportunities (considering different mobility profiles and periods of the day/week) that could benefit from implementing street experiments.

  • Scenario analysis and policy evaluation. It could simulate the potential impacts on local accessibility of a street experiment and evaluate its success in ex-post studies.

The Index calculation is structured of three preliminary analytical steps: (1) the first concerns the construction of the street network detailed with information on the morpho-functional characteristics of the streets. The approach considers three types of users based on their mobility profiles with different travel speeds and needs: pedestrians, cyclists, people with reduced mobility. Thus, the Index is calculated starting from the OpenStreetMap (OSM) street network (or graph), subsequently detailed through open data and direct surveys. As a result, IAPI identifies the intrinsic characteristics and technical performances of the streets and integrates them into the graph to evaluate accessibility based on the capabilities and needs of the three users. (2) The second step entails collecting and mapping the basket of services based on their features and availability at different times of the day and week. Hence, the approach considers a basket of daily services indispensable in the view of providing forms of basic accessibility and “activity participation”. Conversely, public transport stops are among the daily service through which it is possible to reach further opportunities outside the neighbourhood. (3) “What is basic” depends on the needs of the inhabitants and the city users. In this first experimentation, the interaction phase with the inhabitants was missing. However, in the subsequent phases of the research, the activation of focus groups and the use of the Commonplace interactive platform will detail the portfolio of services more related to the needs of the local communities.


Methodological approach Ⓒ Politecnico di Milano

The Index measures the accessibility levels via isochrones. The accessibility index is carried out in GIS, with thresholds of 5, 10 and 15 minutes that identify the catchment areas of each service of the basket and restrictions (barriers, interrupted connections) that limit accessibility. The subsequent operation is calculating an accessibility score that sums the different levels of accessibility to all the baskets of services. To carry out this complex operation was created a hexagonal grid dividing the space with an area equal to the area of the blocks (census tracts) in the study area. For the cumulative principle, the result is a score where higher values correspond to high levels of accessibility by proximity. On the contrary, the hexagons indicating lower scores refer to poorer levels of accessibility by proximity. Then, the Index is replicated for each of the three profiles of users distinguished by different costs and speeds throughout the network.


Comparison between pedestrians and people with reduced mobility accessibility (E.g. Supermarkets). Ⓒ Politecnico di Milano

The experiment aimed to test the relevance of the proposed approach in offering a synthetic representation of areas that suffer from poor accessibility to essential services and to understand if the problem is attributable to the lack of these services or the quality cycle-pedestrian paths. A further purpose of the experimentation, beyond the specific results obtained in Crescenzago, is to evaluate the transferability of the approach to other contexts and cities. The results are strictly linked to the information that characterised the network. However, the level of detail achieved through field surveys makes the index construction process demanding and complex, limiting its transferability. Since the Index, for the research, aims to be a tool that is easy to implement, transfer and use by policymakers, we are working to optimise the use of OSM with limited integration operations, less expensive than an extensive survey.