Through selected case studies, this paper illustrates the way in which the inadequate visibility of road signs and pavement markings at night contributes to wrong-way driving. A concept termed the keg of legibility, which delineates the limits of nighttime visibility under low-beam headlights, is described. The application of the keg-of-legibility concept to the placement of signs, markings, and additional devices that help guide the motorist through the intersection of a four-lane divided highway and another road is discussed. Examples of wrong-way entry on roads having poor geometrics are used to emphasize the need for such guidance.