Perceptual Judgments of the Efficacy of Visibility AIDS (Extended Abstract)
Authors: Szubski Ellen C. , Fekety Drea K. , Edewaard Darlene E. , Tyrrell Richard A. 
Published: September 2018

Introduction. According to the National Highway Traffic Safety Administration (NHTSA), 5,376 pedestrians were killed and approximately 70,000 were injured in 2015 in the US. Seventy-four percent of all pedestrian fatalities occurred in low illumination nighttime conditions, which is a two percent increase from the previous year (NHTSA, 2017; NHTSA, 2015). Pedestrians can wear visibility aids such as retroreflective material to increase their own conspicuity to drivers at night. The conspicuity benefit is maximal when the retroreflective material is strategically positioned to highlight the pedestrians’ “biological motion” (e.g., Wood, Tyrrell, & Carberry, 2005).

Unfortunately, research indicates that most pedestrians are unaware of their own visibility and tend to overestimate their own visibility to drivers at night. However, upon hearing an educational lecture about nighttime visibility and retroreflection, people are more willing to purchase conspicuity-enhancing clothing (Borzendowski et al., 2014). Thus, it is apparent that education is key to increasing awareness of the conspicuity issues at night and therefore pedestrians’ safety.

To our knowledge, typical pedestrians’ understanding of retroreflective and fluorescent materials has not been explored empirically. We hypothesized that typical roadway users do not understand the qualities of the retroreflective and fluorescent material until they see them under specific nighttime conditions. Further, we hypothesized that more in-person interaction with visibility aid materials would lead to more accurate judgments of their utility. The purpose of this study was to quantify observers’ judgments of visibility aids in a simulated nighttime setting before and during a visual demonstration.

Methods. Eighty-four (84) participants, each of whom met pre-determined visual performance criteria, were included in the analysis. The Clemson University Institutional Review Board approved all procedures.

This study followed a mixed factorial design. In the “pre-demonstration” phase, each observer inspected each of the nine test materials using one of three material presentation modes (Wall, Fixed, and Flexible). For each of the nine materials, the task was to provide a numeric estimate (magnitude estimation) of the brightness that the material would display during the demonstration. Following this, the demonstration began and observers provided new magnitude estimates for each of the nine materials.

The 4” x 4” (10.2 cm x 10.2 cm) stimuli were four retroreflective (black retroreflective (hereafter “retro”), blue retro, purple retro, and silver retro) materials, four diffuse reflective (black, blue, purple, & silver) materials and one fluorescent material (yellow fluorescent). Experimenters had, in advance, perceptually matched the chromatic appearance of the retroreflective and paper materials (black, blue, purple, and

silver) so that the chromatic appearance of the paper stimuli were similar to the retroreflective stimuli when viewed in room light. During the demonstration, however, each of the retroreflective materials appeared to be white/silver because their appearance chromatically matches that of the light source illuminating them.

The observer sat in a chair positioned 20 feet (6 m) from the wall where the material samples were mounted for the demonstration. The observer was presented with the nine material samples using a new random sequence. Presentation of that material had three modes of interaction with the material: placed in the observer’s hand and easily manipulated (Flexible); placed in the observer’s hand and fixed to a rigid piece of cardboard (Fixed); placed on the wall 20 feet (6 m) away with no personal interaction (Wall). Each of the nine materials was presented in a predetermined randomized order for both the pre-demonstration and the demonstration phase. For the pre-demonstration phase, observers were asked to predict how bright each of the nine samples would appear when the room lights in the lab were turned off and only a desk lamp, positioned next to the participant, illuminated the sample. For the demonstration phase, observers were situated in a chinrest while still sitting in a chair positioned 20 feet away from the opposing wall of the lab. Observers then viewed each sample in “demonstration phase” (i.e., mounted on the wall and illuminated by the lamp). Observers provided a second magnitude estimate of the brightness of each material. After the experiment, observers competed a survey of their clothing and visibility aid choices during outside nighttime activities.

Results. For brevity, only results that are directly relevant to the hypothesis under investigation are reported here. A mixed ANOVA tested the effects of material type, presentation mode, and presentation phase on the brightness magnitude estimations of each material used. There were three important findings. The most important finding is a significant interaction between presentation phase and material type, F(4.60, 372.79) = 213.77, p < 0.001, partial η2 = 0.73. The

second most important finding is the significant three-way interaction between presentation phase, material type, and material presentation mode, F(9.20, 372.79) = 5.50, p < 0.001, partial η2 = 0.12. The third most important finding is the significant interaction between material type and material presentation mode, F(6.86, 372.79) = 5.17, p < 0.001, partial η2 = 0.11.

In the survey analysis, 61% of observers reported in the post experimental questionnaire that they were frequently outside at night. Approximately 67% (67.1%) of observers reported that during the past week, they wore light-colored clothing while outdoors at night. Of these, 47% reported that they wore light-colored clothing because it was what they were already wearing during the day while only 25.5%

reported wearing light colored clothes for safety reasons. Only one observer from the sample (0.01%) reported wearing a reflective vest outside at night. Seven percent (7.1%) of observers reported wearing fluorescent colored clothing outside at night with 20% of these reporting that this was motivated by safety reasons.

In ranking the usefulness at night of the following items: light-colored clothes, retroreflective vest, fluorescent colored clothes, shoes with reflective patch on them, clothes with reflective patch on them, and flashlight, observers ranked the retroreflective vest as being most useful and the light-colored clothes as being least useful.

Discussion. This study found that observers are not fully aware of how retroreflective materials function or how they can enhance the ability of drivers to see a pedestrian ahead. We found that naïve observers who closely inspected and touched retroreflective material more accurately judged its value than did observers who saw it from a distance. The methods of this study proved crucial to the study’s results, which indicate that although observers are generally unaware of the benefits of visibility aids they can better ascertain the benefits from touching and studying the material. The post-experimental survey showed that participants are somewhat aware of the appropriate clothing to maximize visibility at night but did not report actually using the appropriate clothing. This highlights a lack of appreciation for the visibility problem at night. Additional studies are needed to further explore observers’ understanding of nighttime visibility problems and to find effective interventions that encourage road users to maximize their own conspicuity at night.