I never knew that the Department of Transportation(DOT) called upon AIGA to create the set of directional icons we see everywhere. DOT called upon AIGA to create a universal set of directional/informational icons once they realized that there was a need for them. They compiled a list of images that had been used all across the globe from everywhere from airports to local cities. AIGA selected a team of 5 lead designers to head this project. Once finished they had created a set of 34 icons with 16 more added later. This was one of the first projects that got the Presidential Design Award.
SOURCES: IDSGN, AIGA.