I have seen one before when I was younger. The gentleman that was using it was just riding up and down a dirt road. I assumed that it was for makeing dirt roads more stable. And compacting the dirt. Very cool picture. Thanks for the share kinda brought me back to my younger years for a minute.
Thanks for your comment @raybrockman, looks like it's a "soil compactor" an old one, according to @everittdmickey!