In context of overlay "Surfaces" – Middleton Bike Path (Cycle Path) – https://osm.org/way/220309681 via StreetComplete 57.1:

Horses prohibited on this section of the path (Boise St. to the roundabout south of here). Presumably they are allowed elsewhere (droppings seem to confirm this).

Attached photo(s):
https://westnordost.de/p/200571.jpg