Visual control of steering without course information.

An analysis and experimental evidence are presented that the visual control of steering in following a straight demarcated path is possible even when information about the direction of one's travel (course) is not available. Two likely sources of optical information available to observers are considered, bearing and splay, that might be used for steering under these conditions. In an experiment involving a computer-driven driving simulator, observers attempted to steer a straight path while subjected to lateral perturbing forces. When only bearing and its time derivative, motion parallax, were available, performance fell off as expected with the optical gain of motion parallax as the preview distance of the viewing aperture was varied. When splay angle and its time derivative, splay rate, were added to the display, performance generally improved and remained relatively constant with changing distance of the viewing aperture, as expected because of the constant optical gain of splay rate. Making course information available by adding point features to both displays improved steering performance only in the motion-parallax conditions.