Gaze behavior while crossing complex intersections.
BACKGROUND: Crossing the street is a complex task that involves gathering, processing, and acting on information that is time dependent. The gaze behavior of subjects has been previously studied on increasingly complex and dynamic tasks such as making tea, walking indoors, and driving. The purpose of this study was to assess how normally sighted people use their vision to cross a street safely. Specifically, we identified the environmental features people look at when crossing two types of intersections. METHOD: We measured the eye movements and head directions of 12 normally sighted people as they approached, evaluated, and crossed a light-controlled "plus" intersection and a roundabout. The primary measures were percentage of fixations and head direction. RESULTS: Crossing the street can be divided into three phases, walking to the curb, standing at the curb, and crossing the street. We found that while moving, subjects fixated primarily on crossing elements and when standing at the curb, they fixated primarily on vehicles. At the plus intersection, fixation behavior corresponded with crossing strategy; the subjects who crossed early fixated on cars, and the subjects who waited for the light to change fixated on traffic controls. At the roundabout, all subjects determined an appropriate time to cross from vehicular traffic flow by directing the majority of their fixations on cars. When moving, the head position of subjects was predominately centered. Subjects also made head turns in both directions before crossing and directed the head toward the danger zone while crossing. CONCLUSION: Crossing the street is a complex task that can be described in three phases. Common head and eye behaviors were found near the critical moments of crossing the street. Fixation behavior was closely related to street crossing behavior.