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Joanne Wood, Ralph Marszalek, Trent Carberry, Philippe Lacherez, Sumanth Virupaksha, Michael Collins; Effects of refractive blur and clothing on night-time pedestrian visibility. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1523. doi: https://doi.org/.
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To investigate the effects of refractive blur on night-time pedestrian recognition and whether clothing that has been shown to improve pedestrian conspicuity is robust to the effects of blur.
Twenty-four visually normal participants (12 younger M=25.6 ± 5.2 years and 12 older adults M= 77.6 ± 5.5 years) drove an instrumented vehicle around a 1.8 km closed road circuit at night with 3 levels of binocular blur (+0.50 D, +1.00 D, +2.00 D) compared to a baseline condition (optimal correction). A pedestrian walked in place on the course and wore either normal clothing (gray pants and top), black pants and top with a retroreflective vest, or the same top and vest with retroreflective tape positioned on the extremities in a configuration that conveyed biological motion (known as “biomotion”). Participants pressed a vehicle-mounted response pad when they were first confident that a pedestrian was present; each participant drove around the track 13 times (4 vision conditions x 3 pedestrian clothing conditions randomized + 1 practice trial).
Refractive blur and pedestrian clothing had a significant effect on pedestrian recognition distances (p<0.05) and there was a significant two-way interaction between these factors. Overall, recognition distances were significantly reduced by all levels of blur compared to the baseline. In all blur conditions, a pedestrian wearing the “biomotion” clothing was more recognizable than either the pedestrian wearing the retroreflective vest or normal clothing, and the pedestrian wearing the retroreflective vest was more recognizable than when wearing normal clothing, although the magnitude of the difference became smaller with increasing levels of blur. These effects were greater for younger adults, older adults showing generally shorter recognition distances and therefore smaller effects of either clothing or blur. In the absence of blur, the pedestrian wearing biomotion clothing was recognized at an average distance of 173 m compared to 18 m in the normal-wear condition (almost 10X the distance).
Even small amounts of blur have a significant detrimental effect on night-time pedestrian recognition. Biomotion configurations of retroreflective clothing represent a highly beneficial visibility aid which are effective even under moderately degraded visibility conditions, and improve the recognizability of pedestrians for both older and younger drivers.
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