Visibility and Conspicuity of Detectable Warnings for Pedestrians with Visual Impairments

Detectable warnings are standardized tactile walking surfaces located at the end of curb ramps and train platforms to identify the potential hazard. A study was conducted to determine which detectable warning colors and patterns are visually detectable and conspicuous to pedestrians with visual impairments and to provide recommendations related to color, pattern, and contrast of detectable warnings for placement on sidewalks. Fifty individuals with low vision viewed each of 13 detectable warnings individually on four different types of simulated sidewalk. The set of detectable warnings included both solid colors and black-and-white patterns. The outcomes of interest were visual detection distance, participants' descriptions of detectable warning colors, and participants' ratings of each detectable warning's conspicuity against a particular simulated sidewalk. Detection distance results indicate that pedestrians with visual impairments were able to see most combinations of detectable warning and sidewalk from 8 ft away, but fewer were able to see them at greater distances. Detectable warnings that were similar in color to the sidewalk were seen by few participants, indicating that visual cues provided by the truncated-dome texture itself are not sufficient to ensure visual detection. The luminance contrast between the detectable warning and the sidewalk was an important factor for predicting the likelihood that a detectable warning would be seen. Besides luminance contrast, regression analyses indicated that some other characteristics of detectable warnings were generally associated with high detection rates and high conspicuity ratings, including color (reds and yellows rather than achromatic) and reflectance (lighter colors rather than darker colors). Additional recommendations for detectable warning visual characteristics are provided.