As John&Bet said, you will be charged a fee if you don't have a pass because the byway runs through a National Park. The byway is paved, but you might want to also takes Sage Creek Road (590) that runs from the byway to the. West end of the park. It is gravel, but a good road. Being less travelled, this is where we saw ALL the wildlife - bison, bighorn sheep, antelope. The only wildlife we saw on the actual designated byway was the prairie dogs, although I'm sure others have sometimes seen all the wildlife species on the byway.
You may want to also visit the minuteman missile site just outside the park as well. Exit 131 off of the interstate.