RouteCheckr: Personalized Multicriteria Routing for Mobility Impaired Pedestrians
Thorsten Völkel, Gerhard Weber · 2008 · Proceedings of the 10th International ACM SIGACCESS Conference on Computers and Accessibility (Assets '08) · doi:10.1145/1414471.1414506
Summary
This paper presents RouteCheckr, a client/server system for personalised pedestrian navigation that calculates routes optimised for multiple criteria relevant to mobility impaired users. The authors identify three key shortcomings of existing navigation systems: map data designed for cars that omits pedestrian paths, route optimisation based on a single criterion (distance or time), and no adaptation to individual user needs. The system addresses these through two innovations: multimodal annotation of geographical data, where users collaboratively contribute accessibility information (safety ratings, obstacle locations, orientation features, environmental conditions) to enrich existing maps; and a modified Dijkstra's algorithm that incorporates multiple weighted criteria into route cost calculations. A survey of 88 visually impaired and blind respondents informed requirements, with 75% confirming willingness to contribute annotations. The annotation framework preserves temporal correlation (construction sites are temporary), user group association (blind and wheelchair users perceive barriers differently), and spatial relations (orientation of photos matters for navigation guidance). The system uses a weighted addition cost function where criteria values are normalised within each algorithm iteration, allowing bipolar criteria like safety and distance to be balanced against each other.
Key findings
The personalisation mechanism allows users to rate the importance of each criterion on a 5-point Likert scale, which is converted to weights in the cost function. The paper demonstrates through worked examples how changing user preferences shifts route selection — a user prioritising safety (rated 3) over length (rated 1) gets routed via a safer but longer path, while equal weighting favours the shorter route. The time-dependent annotation weighting scheme ensures newer ratings carry more weight than older ones, addressing the reality that environmental conditions change. This also mitigates malicious ratings, as outlier annotations have decreasing impact as more legitimate ratings accumulate. The prototype was tested on the Technical University of Dresden campus using purchased georeferenced map data that required manual preprocessing to include sidewalks and footpaths. Simulations showed that the linear correlation of criteria costs produced comprehensible results — safer/more accessible routes fell within the 500-1000 metre maximum acceptable detour stated by survey respondents. The authors note that annotations can have opposite implications for different user groups: lowered curbs indicate accessibility for wheelchair users but represent a hazard for blind pedestrians who rely on tactile curb detection.
Relevance
This paper anticipates the crowdsourced accessibility mapping movement that has since grown significantly through projects like Wheelmap and AccessMap. The core insight — that mobility impaired pedestrians are not cars, and that optimal routes depend on individual capabilities and preferences, not just distance — remains fundamental to accessible navigation. The multicriteria algorithm design is notably thoughtful in handling real-world complexity: criteria can conflict (safety vs. distance), annotations decay in relevance over time, different disability groups interpret the same physical feature differently, and malicious data must be tolerated without corrupting results. For practitioners, the privacy-preserving design (annotations linked to user groups, not individuals) offers a model for collaborative accessibility data systems. The observation that existing commercial navigation systems for blind users (Trekker, Sendero GPS) still optimised only for distance highlights how far accessible navigation still had to go — and while modern mapping has improved, truly personalised multicriteria routing for disabled pedestrians remains an active research area.
Tags: navigation · wayfinding · wheelchair accessibility · visual impairment · mobility · personalization · crowdsourcing · algorithms · pedestrian navigation · urban accessibility