The Pink Tree Toilets of Interstate 70

Interstate 70 in Utah is a beautiful freeway. It really hurts me to say this because I am a dedicated freeway shunner. It especially hurts me because I-70 tramples over US50, my favorite road. US50 goes from Ocean City Maryland to Sacramento California in a straight run across the country East-West. Most of it is still two lane, though of course this is changing. But I cannot evade the truth. The lovely curves of the freeway enhance the spectacular beauty of the brilliant, broken land. Remnants of old 50 sometimes appear inconsequentially alongside.
The things that puzzle me though, are the pink tree trunk like toilets at some of the rest stops. I think they are all out of use now. I am intrigued. I hope they will be retained as historic objects,but I suppose they won't be. Who designed them and why? There are very few trees of any girth on that stretch of road, so they weren't intended to match the environment.

Yesterday I was sweating in a sun dress, desperately searching for shade as I waited for my van to be fixed (It didn't happen). Today I am COLD dammit. Couldn't we just have a few temperate days?