From the Chicago Tribune, by Mary Umberger, Business section:
Chicagotribune.com: "Who knew? I never realized there was a term for all of those signs that fill many intersections, touting such wonders as a way to build wealth by working at home, garage sales and, yes, new-home developments -- the latter particularly prolific at Chicago expressway exits. Apparently, according to the Ft. Wayne News-Sentinel, they are 'road lice.' The paper was discussing such signage recently after Ft. Wayne's elected officials strengthened laws prohibiting the placement of signs -- including campaign posters -- on its rights of way."
Fort Wayne: Leading the way in ridding the world of Road Lice.