SomeoneElse
Well public bridleways down service roads aren't that uncommon...
Looking at the tagging on https://www.openstreetmap.org/way/445974499/history , I think that someone's tried to indicate that it is a public bridleway by adding a tag "horse=designated".  A better way of doing that would be by adding a "designation=public_bridleway" tag; that way maps that show public bridleways will show it as one.
Best Regards,
Andy
