The term is most commonly associated with diagrammatic signs installed ahead of forks in controlled-access highways to indicate the destination of each lane.
Diagrammatic signs are specified in the Manual on Uniform Traffic Control Devices developed by the United States Federal Highway Administration, as one of several options for exits and splits on multilane freeways.
A simpler kind of diagrammatic sign without lane detail is allowed for indicating a series of exits along a conventional street or roundabout.
By contrast, California, Minnesota, Ohio, and Mississippi make extensive use of pull-through or arrow-per-lane signs to indicate lane assignments.
Simplified diagrammatic signs would continue to be used at roundabouts and other conventional streets where lane detail is not required.