Perception of Pedestrian Traffic Signals by Pedestrians with Varying Levels of Vision

Abstract

This study evaluates the usability of pedestrian signals by persons with varying visual acuities under different conditions of symbol size, crossing length and type of background behind the pedestrian signal. While viewing photographs presented on a computer monitor under unimpaired viewing conditions (approx. 20/20 visual acuity) and under simulated visual impairment (approx. acuities of 20/100 and 20/300), participants attempted to determine the pedestrian phase (Walk or Don’t Walk) and to report the number presented by the countdown timer display. Performance on the phase discrimination task by those with simulated 20/300 acuity and with 9 and 12 in. high symbols often resulted in performance which was little better than chance despite a highly controlled environment (i.e., no moving vehicles or environmental distractions) and signals which were subjectively in excellent working condition and of high visibility (i.e., good luminance/contrast, no glare). Reading the countdown display was essentially impossible. Participants with simulated 20/100 acuity were rather successful with regards to phase identification – averaging better than 87% correct under all stimulus conditions – but room for improvement exists as compared to performance in the 20/20 condition. Reading the countdown display was difficult for participants with simulated 20/100 acuity – averaging between 6.5% and 58.5% correct under the various stimulus conditions. The effect of different backgrounds on the usability of the signals, as well as the implications of the findings with regards to signal size and crossing length on the current signals standards, are discussed.

People With Central Vision Loss Have Difficulty Watching Videos

“…Some of what is known about the relationship between CVL and its effects on task performance comes from studies that have simulated vision impairment. Commonly used simulations include optical defocus (refractive blur),12–17 diffusive filters,17–22 and image blur (though image processing) 15,16,20–24. These may resemble the “initial stages of sudden onset, acquired visual loss”18 due to cataract, keratoconus, corneal scarring, or uncorrected refractive error in that their primary effect is a uniform reduction in image resolution across the visual field.…”

“…These may resemble the “initial stages of sudden onset, acquired visual loss”18 due to cataract, keratoconus, corneal scarring, or uncorrected refractive error in that their primary effect is a uniform reduction in image resolution across the visual field. Such simulations have been used to study reading,13,14,19,25 pedestrian mobility,15–17 postural stability,22 gaze perception,16 eye–hand coordination,24 and driving 17. In addition, “visual impairment simulators,” which can be found at trade shows or in the laboratory,26,27 have been used to study way-finding,28 pharmacy education,27,29 and the impact on the empathy of medical residents 30…”

“…Optical defocus places objects at a depth plane that is out of focus on the retina 12–17. Studies that have used these simulations suggest that they may impair viewers comparably to those with low visual acuity and low vision for certain tasks 18,20–22,31.…”

“…Studies that have used these simulations suggest that they may impair viewers comparably to those with low visual acuity and low vision for certain tasks 18,20–22,31. In the second study, we induced blur by using defocus lenses (refractive blur), which had been previously used to simulate impaired vision 12–17. We examined whether the effects of CVL simulated with optical defocus were similar to those of real CVL by using IA scores.…”

Determining Confusion for Traditional and Experimental Pedestrian Signals in Rural and Suburban Areas in the United States

“…Despite the benefits, vision impaired pedestrians face a particular challenge when using these signals. Scott et al (2012) found that people with vision acuity issues successfully identify phase changes with 87 percent accuracy, but they have a significantly more difficult time recognizing the countdown display.…”