University of California Transportation Center

The wallpaper illusion, first described over a century ago, can occur when a person with normal binocular vision views a pattern that is periodic in the horizontal meridian of the visual field. Escalator treads present such a pattern. Evidence is presented favoring the view that disorientation experienced by escalator riders is caused by this illusion. Possibly some of the estimated 60,000 escalator falls occurring in the United States each year are linked to it.