As one of the Fresnel lens, the reflector works the same way to distribute the light. It forms a twin Fresnel lens structure by using the direct light of the street light. This structure makes most of the light go in a horizontal direction. The light above the horizontal is scattered by the prisms. With the reflector, the light can also illuminate as large an area as it can in the desired direction, preventing glare.
After the streets apply LED street lights, I find the light color is colder than yellow. As LED street lights can change color, why not change to warm white?