Disability mobility studies generally refer to qualitative, individual-oriented assessments of the barriers endured by a predetermined segment of the population. More recently, city-scale, mainly quantitative studies arose, measuring accessibility for various impaired publics. These last contributions allow standardizing, comparing, and locating accessibility inequalities. Yet, they generally focus on legal standards or norms, and lived experiences are set aside. Moreover, only a small part of the impaired population, mostly wheelchair users, is usually considered. However, in cities like Strasbourg, where the underground-free Public Transport (PT) network backbone is the 1994 tramway, built according to the People with Reduced Mobility (PRM) standards, PT accessibility is still not the same for everyone. Physical, social, and cognitive barriers still challenge i) the inclusiveness of PT stations and rolling stocks, and ii) the pedestrian path, which is often a forgotten part of a PT trip. Not only the usually labeled PRM are impacted, but a wide range of what Global Health studies generally name “fragile populations”.

Consequently, the two aforementioned methods, scopes, and assumptions must be combined to genuinely measure accessibility gaps for several fragile publics. Following a people-centered approach to the concept of accessibility, we consider the different natures of accessibility barriers, framed in an inaccessibility iceberg.

The proposed method then consists of using Face-to-Face interviews, Go-along interviews, and Focus Group Discussions with fragile populations (four target groups consisting of the physically disabled, the visually impaired/blind, the elderly, and the economically disadvantaged) to set the parameters for intra-urban accessibility measuring. Then, the modeling and routing steps are carried out thanks to OpenTripPlanner, linked with GIS mapping tools. The pedestrian routing is enriched by a specific database taking into account street obstacles, narrow sidewalks, stairs, etc. Several quantitative accessibility indicators are provided and displayed in a digital atlas.

The resulting accessibility gaps regarding intra-urban mobility to a selected set of Points of Interest in Strasbourg will be analyzed. Furthermore, the virtues, challenges, and limitations of this mixed-method approach in terms of data availability, context-sensitivity, representativeness, and justice perspectives will be discussed.

The design of a public transport (PT) networks - e.g. long routes from one city edge to another city vs. short routes from the city edge to a trunk line - influences whether PT users would experience direct or indirect routing (i.e. without/with transfer(s), respectively). Transfers can add time to journeys. They are also known to be painful to a certain extent, depending on the concrete conditions (e.g. stop design, horizontal and vertical distance between stops, PT frequency, etc.) and the characteristics of travellers (age, physical condition, etc.). In other words, transfers induce "disutility", which can be estimated (typically through revealed or stated preferences) and ultimately translated into so-called perceived travel time (as opposed to real or theoretical travel time). It is also known that of all the barriers that prevent disabled people from using public transport, transfers are key, as they cause even more inconvenience and create more risks of not being able to board or disembark. The design of PT networks is thus far from neutral for PT users.

In this context, this research proposes an investigation using Brussels as a case study. PT routes will be estimated between 724 districts to about 20 points of interest spread over the city. This will be done thanks to 5R software fed by GTFS files (PT network and timetables) and OpenStreetMap for walking in public spaces. The estimated itineraries will make it possible to correlate travel time with the number of transfers. Travel times will then be analysed from three perspectives:

1) Real or theoretical travel times

2) Perceived travel times (based on parameters provided by the regional administration)

3) Extrapolation of perceived travel times to disabled people with physical impairments (through interviews with their representatives).

When analysing disabled mobilities, a central focus is given to the lack of accessibility of the built environment, as with unavoidable stairs or wide open spaces with no tactile markings on the floor. This allows one to look at the missing, inaccessible or unreachable parts of the network, and is applicable whether one considers public transportation systems or road networks. Often enough, this reveals a large difference between disabled and abled mobilities, but this analysis can be pushed much further. Indeed, a central although discreet aspect of many such network are their redundancies (or fault-tolerance). Construction work on a single metro line in a major city disturbs mobilities but does not prevent them altogether, nor does a crowd in any given street fully prevent pedestrian flow around it. Following Kaufmann's interpretation of motility, it seems instead that many users have a level of competence which allows them to compensate for unforeseen obstacles and detours to reach their destination.

For disabled users, the situation is quite different, as the set of potential obstacles which can impede circulation increases, varying with the specific impairments. We propose here to look at how both the real fragility of the network and the perception of said fragility can affect the disabled users' competence. First, users need an additonal form of competence, corresponding to the need to navigate not only the transport network but also the assistance services. This includes both competence in getting needed usual assistance, knowledge of backup systems, and potentially familiarity with the corresponding policing of disabled bodies. Second, the increased risks and costs reduce the extent to which users can safely explore the network, which limits competence building. Finally, the more fragile a network is, the more knowledge is required to safely traverse it, which means that the required level of competence increases.

This study evaluates assesses the impact of 15 contrasted scenarios that improve the inclusiveness of the Brussels’ public transport (PT) network in terms of access to the city for disabled people. The scenarios are based on improved design of both surface/underground stops and of the vehicles, and they focus on step-free access as well as tactile paving. They vary in ambition (from low to high) and on spatial coverage (spread vs concentrated).

Inputs are GTFS files and OpenStreetMap. Itineraries from all 2,174 PT stops to 20 points of interest spread across the city are estimated thanks to OpenTripPlanner. Key outcomes are travel time, number of transfers and walking distance.

It is expected that (1) the improvements are very heterogeneous across the scenarios but also depending on the departure and arrival points; (2) the best scenarios are those that jointly improve the main hubs and the entire underground network, as opposed to scenarios with upgrades scattered across the city or limited to some specific routes. This will be validated or invalidated by the EUGEO conference.