We propose functional specifications for a localized verbal wayfinding aid for blind pedestrians, in simple and structured urban areas. A user-centered design approach, that is, the analyses of route descriptions produced by blind pedestrians, allowed first to evidence verbal guidance rules and then to elaborate route descriptions of unfamiliar paths; their efficiency was confirmed. We found that specific database features are streets, sidewalks, crosswalks, and intersections and that guidance

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... unctions consist of a combination of orientation and localization, goal location, intersection, crosswalks, and warning information as well as of progression, crossing, orientation, and route-ending instructions; they have to be provided between 5 to 10 meters before an intersection, after crossing, at middle block, and after entering a street. Last, verbal guidance is pos-Florence Gaunet is a cognitive psychologist with an interest in spatial wayfinding by blind pedestrians; she is a researcher in the Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur at CNRS. Xavier Briffault is a computer scientist with an interest in natural language processing; he is a researcher in the Laboratoire d'Informatique pour la Mécanique et les Sciences de l'Ingénieur at CNRS. sible in simple and structured urban areas, with no localization aid, and is optimal within 5 meters' precision. The outcomes and limits of the requirements of the navigational aid evidenced are discussed.