Road studs, also called "cat's eyes" or "raised pavement markers," are safety devices embedded in roads that reflect vehicle lights to improve lane visibility at night or in bad weather, guide drivers, and sometimes act as rumble strips. They come in various colors (white for lanes, red for edges, yellow for separators) and can be passive reflectors or solar-powered LED lights, enhancing safety by making road markings clearer and alerting drivers to changes in the road.