Two-Direction Large Arrow, Black and White
The Two-Direction Large Arrow sign shall be a horizontal rectangle. If used, it shall be installed on the far side of a T-intersection in line with, and at approximately a right angle to, approaching traffic. The Two-Direction Large Arrow sign shall not be used where there is no change in the direction of travel such as at the beginnings and ends of medians or at center piers.
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)