Misperception and visual illusion as contributing factors in nighttime crashes

Abstract

ABSTRACTForensic HFE attempts to understand and explain factors that may have contributed to specific human-system failures or injury events. It involves, by definition, after-the-fact review of available evidence as well as activity analysis of all involved parties and possibly site inspection, when warranted. An often-overlooked explanation for road crashes is visual misperception and illusions, which come in a variety of forms. The possible involvement of visual misperception in crash causation can be evaluated during a comprehensive site inspection under conditions that correspond as much as reasonably possible to the actual conditions that existed at the time of the crash. Two case studies are described that illustrate the value of site inspection in uncovering the possible contribution of visual misperception in these nighttime fatal crashes; case 1 involving visual illusion, and case 2 involving signal ambiguity. These cases demonstrate that site visits at night can be helpful in uncovering important visual phenomena that might not otherwise be apparent.