Retroreflectors can be embedded in the road (level with the road surface), or they can be raised above the road surface. Raised reflectors are visible for very long distances (typically 0.5–1 kilometer or more), while sunken reflectors are visible only at very close ranges due to the higher angle required to properly reflect the light. Raised reflectors are generally not used in areas that regularly experience snow during winter, as passing snowplows can tear them off the roadways. Stress on roadways caused by cars running over embedded objects also contributes to accelerated wear and pothole formation.