Evaluation of the Differentiability of Newly Developed Low-Profile Bar- and Dot-Shaped Tactile Walking Surface Indicators

Recently, the authors have developed the low-profile bar-shaped and dot-shaped TWSIs used in the environments in which irregularity of floor/ground surface can be virtually ignored. Since both bar- and dot-shaped TWSIs are used together to constitute tactile pathways for the vision impaired persons, the authors examined the differentiability between the low-profile bar- and dot-shaped TWSIs in the present study. Ten visually impaired participants served as experimental subjects. The shape and arrangement of bumps of low-profile bar- and dot-shaped TWSIs for the examination were made based on the bar- and dot-shaped TWSIs standardized in Japan. The height of the truncated cone of dot-shaped TWSIs and the flat-top bar of bar-shaped TWSIs was set to 3.0, 3.5, 4.0 4.5 mm and the top diameter of the dot was set to 12.0 (control), 9.0 and 6.0 mm. To evaluate the differentiability between various bar- and dot-shaped TWSIs, pairs of the same height were used. Subjects were asked to walk from bar-shaped TWSIs toward dot-shaped TWSIs and to stop when they recognized dot-shaped TWSIs. The differentiability was determined by measuring the rate of differentiation. The degree of difficulty on their judgement was measured using four point scale, 1 (easy) to 4 (hard). The degree of confidence on their judgment was also measured using four point scale, 1 (weak) to 4 (strong). The average rate of differentiation was almost 100% regardless of the top diameter and the height. The degree of difficulty in differentiation distributed between1.8-2.7 and decreased with increasing the height of bumps from 3.0 mm to 4.0 mm. The degree of confidence distributed between 2.5 and 3.3 and showed the tendency opposite to the degree of difficulty. From these results, it appeared that bar- and dot-shaped TWSIs lower than 5.0 mm (standard height) and dot-shaped TWSIs smaller than 12.0 mm (control) seem to be useful when they are installed rather flat floor or ground surfaces.