Human
 Factors

Perception Response Time is adapted from the Wickens Human Information Processing Model that outlines the amount of time elapsed between perception of a hazard to the start of a specific motor response. In motor vehicle accidents this is typically taken to be the time between recognition of a hazard to the point at which an emergency-level maneuver is anticipated by the general population of drivers. Perception response time is often used by accident reconstructionists and human factors professionals to determine whether a specific motor vehicle accident is avoidable.

The study of driver vision and gaze locations can be used to pinpoint where drivers tend to look when executing a certain maneuver such as going around a turn or curve, changing lanes, checking their mirrors, or coming to a stop at an intersection. Understanding the driver’s gaze can be key to determining when a driver or pedestrian may have detected and recognized a hazard in their path of travel. Eye Tracking technology can be deployed to determine where drivers look in a specific type of scenario.  

Different motor vehicle accident configurations can yield drastically different response types and amplitudes from drivers. Understanding driver behavior and typical response modalities to a set of accident configurations can be instrumental in determining whether an accident was avoidable and whether an accident occurred at a different severity than what would have been expected.

Line of sight analysis including physical obstruction, shadows projections, color contrast, or lighting intensity is used for determining if a given object is both detectable and recognizable, particularly as a hazard, to a given observer. Physical obstruction can prevent a driver/pedestrian from detecting a hazard by blocking light, however, other less-salient obstructions such as lack of lighting or contrast may also impede an observer from detecting and recognizing an object or hazard.

Nighttime, dark scene, and limited visibility motor vehicle accidents require additional analysis beyond basic accident reconstruction, as hazards presented to an observer will have limited recognition distances, conspicuity, and salience based on light sources, or lack thereof, present at the time of the incident.

When objects are partially or completely occluded, the point at which they become recognizable as a hazard to an observer can be critical in determining when a response should be elicited and what type of response would be expected. Understanding of when a hazard would be detectable and recognizable, such that an observer could glean information from the hazard, can and should be determined by a Human Factors professional.

Pedestrian response times and modalities are often of importance for forensic human factors analysis. How pedestrians respond to stimuli, be it visual, auditory, or tactile, and the location of the stimuli can be used to determine if a given response to typical or not. It can also be used to determine if the pedestrian could have taken action to avoid a given motor vehicle accident, trip, or slip and fall.

For highly atypical or unusual motor vehicle accident scenarios, a driving simulator study can be utilized for determining driver responses to a specific motor vehicle accident. Driver response times, response modalities, and general accident avoidability can be determined internally utilizing our moderate fidelity driving simulator. The driving simulator itself can be programmed to replicate the exact interior of the subject vehicle as well as the subject vehicle performance characteristics.

The Human Information Processing model, as established by Christopher Wickens, is generally thought of as the root to which much of the forensic human factors analysis branches out from.

Determining whether or not a given accident was avoidance for a specific party can be instrumental in determining liability. For certain motor vehicle accidents, avoidance may, or may not be, nearly certain when comparison to the general population and determination of avoidability is best left to an expert in Human Factors.

In path navigation, obstacle avoidance, and pedestrian travel, obstacle avoidance can be determined based on characteristics of the obstacle as well as the path including but not limited to shadow projection, contrast, lighting, pedestrian eye position, vertical discontinuity, and path normality.

Just because a physical response was made; be it steering, braking, or a combination of both, or doing nothing, does not necessarily mean it was optimal or even typical for a given situation. Different motor vehicle accident configurations tend to illicit different responses from drivers. Determining which response type is optimal and probable can be determined by a human factors expert.  

Photographs and videos of an incident scene don’t necessarily accurately depict conditions as they were at the time of the incident. Differences in camera shutter speed, aperture size, or iso sensitivity can have an effect on how bright photographs and videos appear. A human factors expert can photograph and take videos of a scene that accurately replicate relative brightness and lighting conditions when the scene inspection is conducted.

Projection and analysis of intensity of headlight beams can be utilized when determining whether or not a target was sufficiently illuminated in order to detect and recognize the target as a hazard. A human factors expert can also analyze the headlamp or taillamp bulbs to potentially determine whether or not lights were turned on at the time of an incident.