many states in snow-prone areas of the midwest and northeastern united states use stimsonite reflectors placed into protective metal castings, which allow them to be plowed over without being dislodged from the road surface. these pavement markers are usually augmented with reflective paint and delineators placed on plastic or metal posts at regular intervals along the edges of the road. in california and other locations in the southwest united states that experience occasional but significant snowfall, the stimsonite reflectors are placed into recessed pockets in the roadway, which allows visibility during dry weather but permits a plow blade to travel across the reflector without dislodging it, with no special protective castings needed.