Size Isn't Everything: The Effects of Size and Brightness of Retroreflective Materials on Nighttime Conspicuity

Abstract

To increase their level of conspicuity, emergency response personnel wear Personal Protective Equipment (PPE) with retroreflective materials. That is, retroreflective materials increase the probability that oncoming motorists will see them. The goal of the current study was to provide empirical evidence regarding the relative nighttime conspicuity of conventional-trim retroreflective patterned garments (which have retroreflective material concentrated on specific portions of the garment) and area-retroreflective patterned garments (which have retroreflective material distributed evenly across the surface area of the garments). The question of interest was whether trim and area-reflective garments that reflect the same amount of light (i.e., equal RI values) provide equivalent conspicuity. At night, subjects seated in the passenger seat of cars approaching a live simulated roadway accident scene attempted to detect and recognize a human form in the road. Across three different levels of RI, the results demonstrate that when area reflective and trim garments reflect the same overall amount of light, area reflective garments provide lower levels of conspicuity than do conventional trim garments. These results suggest that, under the conditions of the current study, the brightness per unit area of retroreflective material needs to be considered rather than simply considering the total brightness of the garment independent of the size of the retroreflective surface-area.