One-Direction Large Arrow, Silhouette
The horizontal alignment signs may be used in advance of situations where the horizontal roadway alignment changes. A One-Direction Large Arrow sign may be used on the outside of the turn or curve. When the Hairpin Curve sign or the 270-degree Loop sign is installed, either a One-Direction Large Arrow sign or Chevron Alignment signs should be installed on the outside of the turn or curve.
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)