When I was young and living in Jersey City, NJ, my old hometown, I took city buses for at least 20 years. Of course, they don't have restrooms inside but Greyhound buses do since they drive long trips non-stop.
BTW, I never forget one day when I got into a city bus and sat down in the back, I noticed the bus driver yelling at me and I told him that I am deaf. Then I started to smell dog poop on one of my shoes and noticed my shoe prints with dog poop on the floor. I was so embarrassed, even though he didn't kick me out. I don't recall but I think the driver cleaned it up immediately. Damn dog owner whoever let the dog poop on the grass at the bus stop.