Analyzing Accessibility Barriers Using Cost-Benefit Analysis to Design Reliable Navigation Services for Wheelchair Users

Abstract

This paper explores 'A to B' routing tools designed to chart accessible routes for wheelchair users. We develop and present a novel measurement framework based upon cost-benefit analysis in order to evaluate the real-world utility of routing systems for wheelchair users. Using this framework, we compare proposed routes generated by accessibility tools with the pedestrian routes generated by Google Maps by means of conducting expert assessments of the situation on the ground. Relative to tools aimed at pedestrians, we find that these tools are not significantly more likely to produce an accessible route, and more often than not, they present longer routes that arise from imaginary barriers that do not exist in the real world. This analysis indicates how future routing tools for wheelchair users should be designed to ensure that they genuinely ameliorate the effects of accessibility barriers in the built environment.

Using Computer Simulations to Investigate the Potential Performance of ‘A to B’ Routing Systems for People with Mobility Impairments

“…It is distinct from the 'within A/B' problem which addresses the scenario as to whether a given location itself is accessible (as opposed to an accessible route to getting there in the first place). For many people with disabilities, pre-existing navigation tools are often inadequate, because they do not reliably accurately provide routes that are accessible to the end user [12,40]. In the real world, accessibility barriers often permeate the built environment, with a recent study reporting averages of over 1 accessibility problem for every 100m travelled in some cities [10], whilst another investigation showed one US city had 80% of curbs that were not ADA compliant [1].…”

“…[50] for summary of trip statistics amongst the general population). We chose accessible bathrooms as landmarks for the reasons given in [40], namely this is a commonly required trip by people with disabilities.…”

“…System. As explained in [40] (see also Figure 3), there are two main types of documentation error that can be made by an accessibility documentation system. The first is to state that a street segment (i.e.…”

“…There are three main types of navigation error (Table 1) that are of concern: (i) providing unnecessarily longer routes, (ii) heading down a route segment that contains a barrier and (iii) reporting that there is no accessible route when one exists. In line with [40] we calculate performance of a tool on a given route by using a distance measure, which is the distance of the route selected, with a further 500m penalty for each accessibility barrier encountered. This estimate is based on a realistic amount of time to select and travel an alternative route that does not contain a barrier.…”

“…Whilst the need for this has already been identified (see e.g. [40]), we are unaware of any widely used accessible navigation system that presents options and routes in terms of risk. The simulations we have presented allow for this risk to be estimated and presented to end users in the context of a navigation system, thus overcoming this hurdle if the accuracy of the documentation tool can be estimated, likewise with the distribution of accessibility barriers in a city.…”