Effectiveness of Lighted Work Zone Apparel: Effects on Visibility

Abstract

In United States, collisions between vehicles and workers in a work zone are a major problem. In 2020, there were 157 worker fatalities in work zone in the United States. Increasing worker conspicuity has the potential to reduce to fatalities by making them more visible to motorists. Retroreflective vests (Class 3) and trousers (Class E) worn by workers in a nighttime work zone are passive in nature; i.e., they require light from oncoming vehicle headlamps to work. The advancement of LED technology has made it easy to install them on retroreflective vests and hard hats to increase their conspicuity. Multiple configurations of LEDs and flash patterns installed on vests and hard hats could be used to increase worker conspicuity. Further, equipment manufacturers are now offering work zone apparel and head protection which incorporate lights into portions of the retroreflective material, or adds light to a specific piece of equipment (hard hats). One of the major benefits is that these do not require external light sources for activation whereas retroreflective material relies on an eternal light source. According to manufacturers, the new apparel and equipment improve visibility, and the pieces are washable. There is also the potential for lighted apparel that uses colors or operating features (such as flash patterns) to further increase worker conspicuity. However, a typical work zone is a visually cluttered with flashing lights on work vehicles. Therefore, it is important that the selected configuration of lights on workers apparel are not masked by the visual clutter in the work zone. The conspicuity of passive (retroreflective material only) and active (both retroreflective and LEDs) apparel in a work zone will help in determining the apparel that would increase the conspicuity of the workers in the work zone. The goal of the current study is to evaluate effectiveness of lighted work zone apparel under realistic conditions. More specifically, the goal is to compare the effectiveness of various kinds of lighted worker apparel (colors, flash patterns, lighted hard hat, etc.) to that of standard retroreflective material under varying visually cluttered conditions. In the current study, the effects of worker apparel and scene clutter on driver visual performance were evaluated under realistic work zone conditions. Driver visual performance was measured indirectly using the detection distance of work-zone workers as indicated by participants as they drove through the simulated work-zone environment. The results of the current study show that lighted worker vests and helmet-mounted lights plays a critical role in increasing the conspicuity of workers in active nighttime work-zone environments with visually cluttered environments. Lighted work-zone vests with white-colored LEDs paired with helmet-mounted LEDs (also white colored), either in flashing or in a steady-on condition, had the longest detection distances. Standard Class 3 retroreflective vests had the lowest detection distances among all the garments evaluated. When workers wore the lighted apparel with red and white LEDs without the lighted helmet, the detection distances were shorter than with the lighted helmet but longer than with the retroreflective vest alone. Based on these results, a combination of lighted garments along with a lighted helmet, preferably in a flashing pattern or steady-on, are recommended to increase the conspicuity of workers in active nighttime work-zone environments.