Metal halide GE highmasts

Some of the last remaining Washington DOT highway lights that are metal halide. The older ones just South of here have already been converted to standard HPS cobraheads. For a while, mercury lamps would show up in those fixtures occasionally. I also find it curious that the double arms are parallel to the roadway, unlike the rest of the lights. These fixtures are used throughout the area but only on small stretches, in clusters of two or three, though mostly HPS.