Hi-viz apparel is designed to make officers more visible and identifiable in the course of performing their duties, particularly when visibility is important for their safety, such as when making traffic stops, directing traffic, or performing other duties near roadways. Hi-viz apparel has two components, one for daylight work and the other for nighttime work. Daytime visibility is aided by the use of fluorescent color, usually fluorescent orange or fluorescent yellow. Studies have indicated the fluorescent yellow stands out better for most people, even those who are color blind. At night, hi-viz apparel uses retroreflective strips on strategic areas of the body. When illuminated by headlights, the stripes are positioned to reveal the basic human shape to drivers. When under streetlights or headlights, the colors so visible in daylight become much less visible, enabling officers who are working in dark areas to appear nearly as dark as their surroundings, so the hi-viz material does not compromise their safety when visibility is not desirable. Officers may carry a tactical cover-up vest when visibility is not desired in daylight. Such vests are typically lightweight slip-on jackets made of a black, nonshiny fabric that can be easily put on when daylight visibility may be hazardous. In a survey of bike officers in preparation for this article nearly all were advocates of wearing the hi-viz apparel all the time, as they believed this is best for their safety, all things considered.