I've never seen a horse get loose, but that doesn't mean it can't happen. Yeah, slow moving vehicles are a hazard, and buggies are no exception to that. They're not a lot different than encountering a tractor, though. Bicycles can make the road interesting too. On Sundays, they're all over the place west of Madison, and you need to figure that every time you encounter a hill, there'll be bicycles on the other side of the crest. Up north, you have the added attraction of many roads not having shoulders. Bikes, buggies, and tractors are in the lane of traffic. All you can do is follow them until you have the opportunity to carefully go around them. The bottom line is that tractors, buggies, and bicycles are legal and a fact of life. Unlike deer, at least they're operated by humans who are (usually) aware of their responsibilities. Deer like to do the opposite of what drivers expect; anything goes with them.