Me neither. This is the only road I've seen this. We actually don't use overhead speed limit signs on the freeways either. They're on regular U-cannel poles on the sides of the freeway.
our older poles are 4X4" wood poles, but they like to use the galvanized U-channel now. The city uses green U-channel poles though. Those look nice, but rust so fast. The glavanized ones are better IMO.
Some older median island signs are mounted on mini signal flasher poles...a relic from when signs were illuminated.