Horse-Drawn Vehicles, Color
Vehicular Traffic signs may be used to alert road users to locations where unexpected entries into the roadway by trucks, bicyclists, farm vehicles, emergency vehicles, golf carts, horse-drawn vehicles, or other vehicles might occur. These locations might be relatively confined or might occur randomly over a segment of roadway. Vehicular Traffic signs should be used only at locations where the road user's sight distance is restricted, or the condition, activity, or entering traffic would be unexpected. If the condition or activity is seasonal or temporary, the Vehicular Traffic sign should be removed or covered when the condition or activity does not exist.
Federal Highway Administration Manual on Uniform Traffic Control Devices for Streets and Highways, 2003 Edition (including 2004 and 2007 revisions) (Washington, DC: United States Department of Transportation, 2007)