Visibility / Human Factors

Jim Sobek | Stuart Nightenhelser

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Our senses link us to the outside world. Vision is the richest of the human senses.  We are highly dependent on seeing to perform many activities such as operating motor vehicles, walking, reading, etc.  Light is the basic stimulus for vision.  Understanding how light behaves in the environment is the first key to understanding visibility.

 In addition, we must understand the optics, the basic physiology of the human eye and how these visual systems process the light stimuli to produce the final perception.
 
Many accidents result from failure to see/notice features within a scene.  Lighting levels, scene contrast and changing scene elements may all be relevant to these failures as well as weather conditions, viewer visual capabilities and viewer attention/distraction.  

In determining whether or not a particular individual could/could not have seen certain scene features, a site investigation is usually required.  During that site inspection, we may collect photographs, video, survey data and other physical measurements.  Also, during this site inspection we may look for signs, visual clutter, and background lighting that might have helped or hindered the viewer.
 
Vehicle examinations may also be conducted to learn which (if any) lamps were activated at the time of the incident.  Photographs will document the vehicle condition, particularly whether active and/or retro-reflective elements would have been of any assistance.  
Mirrors, sight obstructions and other vehicle configuration elements may reveal that the driver’s view was limited at a critical time.  Often, the vehicles involved may be surveyed to assist in later development of graphic simulations and other demonstrative evidence.

CONTACTS: Jim Sobek | Stuart Nightenhelser