The effects of two types of “stop” markers, nine angles of orientation, four vehicle velocities, and their interactions were studied in a dynamic traffic situation. Because “stop” markers are seen in constant transformation in actual driving situations, the experiment studied dynamic conditions in the laboratory by variation of the mentioned factors in short (10-sec.) film clips. Thirty subjects responded to each clip in one of three possible categories: (1) “stop,” (2) “not stop,” and (3) “not seen“ (not detected). Responses of the first two types were then categorized as either correct or in error, based on stimulus orientation. An analysis of variance proved the factors of marker type, viewing angle, and their interaction to be statistically significant, while the factor of vehicle velocity and other interactions proved not significant. More correct responses were produced by the curved marker than by the two-dimensional marker at most angles of orientation and at all vehicle velocities.