Marked crosswalks are usually placed at traffic intersections or crossroads, but are occasionally used at mid-block locations where pedestrian generators are present such as at transit stops, schools, retail, or housing destinations. In the United States, these "mid-block crossings" may include additional regulatory signage such as "PED XING" (for "pedestrian crossing"), flashing yellow beacons, stop or yield signs, or by actuated or automatic signals. Some more innovative crossing treatments include in-pavement flashers, yellow flashing warning lights installed in the roadway, or HAWK beacon—an overhead signal with a pair of red beacons above an amber beacon, when a pedestrian is detected or actuates the device it begins a sequence of amber flashing followed by a solid red, followed by a flashing red phase that allows motorists to proceed, only if the pedestrian(s) are clear of the travel way.