What do white lines on a roadway generally separate?

White pavement markings separate lanes of traffic traveling in the same direction and mark the right edge of the roadway. A broken (dashed) white line between lanes means you may change lanes when it is safe; a solid white line discourages or prohibits lane changes and is often used near intersections or to mark the edge line. By contrast, yellow lines separate opposing traffic. Recognizing the difference — white for same-direction lanes and road edges, yellow for opposing traffic — helps a driver understand the roadway layout. Pavement markings are a tested part of the road-signs section.