Structural obstacles barring access by the physically handicapped to a place, building, installation, or vehicle. Examples: electric switches, door knobs, elevator buttons, drinking fountains, and telephones out of reach of a person sitting in a wheelchair; doors too narrow or washrooms too small to accommodate a wheelchair; unramped curbs and steps without ramps or elevators; visual signals imperceptible to blind persons, not combined with an audible tone; or audible signals imperceptible to deaf persons.
Eisenberg MG. 1995. Dictionary of Rehabilitation. New York: Springer Publishing Company. 375 p. Used with permission.