Tactile guide maps are well-known information support tools for visually impaired people. In a tactile guide map, area information is expressed by use of raised dot patterns and raised boundary lines. Tactile guide map designers must place spaces between these raised dot patterns and raised boundary lines so that tactile guide map users can easily identify the lines. However, there is a lack of quantitative data on the perceptibility of tactile guide map lines. In this study, we investigated

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... influence of the spaces between the raised dot patterns and raised boundary lines on the perceptibility of the tactile guide map lines. We made test pieces with seven different dot distances for dot patterns and five different space distances. The participants included 40 sighted people (20 younger and 20 older ones) as tactile guide map beginner users. The participants were asked to identify the direction of a line, which could be horizontal, vertical, diagonally left up, or diagonally right up. Based on these results, we found that the raised boundary lines were highly easy to identify when the distance between the raised dot patterns and raised boundary lines was greater than 5 mm. This knowledge will be helpful for tactile guide map designers.