Visual accessibility of ramps and steps

Abstract

The visual accessibility of a space refers to the effectiveness with which vision can be used to travel safely through the space. For people with low vision, the detection of steps and ramps is an important component of visual accessibility. We used ramps and steps as visual targets to examine the interacting effects of lighting, object geometry, contrast, viewing distance and spatial resolution. Wooden staging was used to construct a sidewalk with transitions to ramps or steps. 48 normally sighted subjects viewed the sidewalk monocularly through acuity-reducing goggles, and made recognition judgments about the presence of the ramps or steps. The effects of variation in lighting were milder than expected. Performance declined for the largest viewing distance, but exhibited a surprising reversal for nearer viewing. Of relevance to pedestrian safety, the step up was more visible than the step down. We developed a probabilistic cue model to explain the pattern of target confusions. Cues determined by discontinuities in the edge contours of the sidewalk at the transition to the targets were vulnerable to changes in viewing conditions. Cues associated with the height in the picture plane of the targets were more robust.

Recognition of Ramps and Steps by People with Low Vision

“…Trials were blocked by viewing distance. Based on the results of Legge et al, 10 we hypothesized that the low-vision subjects in the present study would perform better at the shorter distances of 5 and 10 ft than at 20 ft and better with the high-contrast black background than the lower-contrast gray background.…”

“…The experimenter obtained informed consent in accordance with procedures approved by the University of Minnesota's institutional review board. The comparison group, from Legge et al, included 48 normally sighted young adults with a mean age of 22 years (see table 2 in Legge et al 10 for further details). These subjects wore blurring goggles, made from Bangerder occlusion foils, which reduced effective acuity to 20/ 135 (mild blur) or 20/900 (severe blur).…”

“…Overhead lighting, representative of typical ambient room lighting, was produced by four rows of three 2 by 4 ft luminaries. For more information about the test space and apparatus, please see Legge et al 10 …”

“…These factors include target-background contrast and lighting arrangements, and also viewing conditions such as distance to target. 10,11 A major aim of the present study was to determine if these results generalize to people with low vision. A long-term goal of our research on visual accessibility is to provide a principled basis for guiding the design of safe environments for the mobility of people with low vision.…”

Low-power depth-based descending stair detection for smart assistive devices

“…From studies on visual accessibility to space for low-vision individuals [5] and the accidents encountered by mobility impaired people [6], constructors are urged to improve stairs and curbs accessibility according to laws and construction guidelines. But, there is still work to be done to facilitate the mobility of individuals with disabilities.…”