To be fair I was speaking from a pedestrian point of view, so not on highways. On actual crossings, apparently to the attention of pedestrians so they'd know where to cross.
Also, the X thing might be obvious for native speakers, but you have no idea how long it took me to figure out was "Xmas" was. "Xing" was slightly faster (I had to figure it out on my own, when I ask people kept laughing >.>) but not by that much. If it was X-ing, then yeah, I'd get it faster, but this way it just looks like a normal word I guess.