The effect of non-visual preview upon the walking speed of visually impaired people.

Abstract Blind pedestrians lack preview of their environment and as a consequence they frequently adopt a slow walking speed. Electronic mobility aids have been designed to increase preview, and thus thinking time, over and above that provided by a long cane, but their ranges have been chosen on somewhat arbitrary grounds. Previous work on the effects of varying preview upon mobility have used artificial indoor environments. In addition, they have used either sight or an aid with a complicated display, the Swedish Laser Cane, as the medium through which to present the preview. The present experiment provided subjects with varying amounts of preview via an electronic mobility aid, the Sonic Pathfinder, as they walked a simple outdoor route. Their walking speed was recorded and found to increase significantly with increased preview. The range of the Sonic Pathfinder has now been increased on the strength of this experiment.