Although there are not many local commuters in the sense that we would think of, the buffalo use the man-made roads just like any other part of the park to get around. If they are in your way, there's really nothing to be done about it except wait. They'll just keep moving until they get to where they want to go. Thankfully, there isn't much grass on the road - giving them little reason to stay.
On the roadside
Driving through Yellowstone, there are plenty of places to pull over and see different things which testify to the volcanic activity beneath. If I remember correctly, there are some rather powerful sulfur pools beneath the rock fence I'm standing in front of. Also, the hill seen behind me wasn't always a hill. Volcanic activity from beneath has caused the hill to be slowly increasing in height over the years.