by Leah S. Hartman, Ph.D., CPO, CXLT, and Stephanie Whetsel Borzendowski, Ph.D., CPSI, CXLT
Introduction
Human Factors is the scientific study of human interaction with their environment, based on the scientific understanding of human capabilities and limitations (e.g., cognition, perception, biomechanics, etc.). A human factors expert should provide an objective analysis of relevant facts and offer insight into human behavior under specific circumstances. While the explanation of these principles may appear familiar to even a layperson due to their personal experiences in similar contexts, they can fail to fully appreciate the complexity of how the environment affects human behavior. Human factors practitioners can examine aspects of the environment and the human independently, and they are uniquely qualified to analyze the interaction between the two.
While practitioners in other disciplines (e.g., engineers, architects, medical practitioners, etc.) can address one of the elements in the human-environment relationship, they typically do not possess expertise (i.e., educational background or training) in the interaction between the two. Therefore, human factors experts can provide attorneys, judges, and/or juries with a framework for understanding an event or incident by relying upon their education, training, and familiarity with the significant body of literature, standards, and regulations within this field.
Civil litigation is ripe with opportunities for the utilization of human factors analyses to further comprehend simple or complex cases. Exemplar areas in which human factors professionals often provide valuable insight include (but are not limited to): falls, collisions, workplace injuries, warnings, drownings, etc. A human factors analysis may be of use in personal injury litigation when there are questions regarding the relative contributions of environmental factors and human characteristics, and the interaction between the two. The following are examples of contexts in which this type of analysis can enrich the comprehension of case facts.
Premises liability
A trip is characterized by a foot unintentionally coming into contact with the ground and/or an obstacle which arrests the forward movement of the foot. In this biomechanical incident, there is typically a rotation of the body in the direction of travel. If the acceleration of the body cannot be arrested, a fall will likely result. Environmental factors typically considered in the analysis of a trip and fall can include geometric proportions of changes in level along walking surfaces and/or the placement of obstacles (permanent or temporary).
A fall that is attributed to a slip occurs when a foot unintentionally slides across a surface, which can result in a loss of balance. Bilateral slips are when both feet are affected. Typically, this results in a feet-forward slip and fall with the trunk of the body falling backwards and landing posteriorly. Unilateral slips occur when the leading foot slides forward as the back foot remains planted. This results in the legs splitting, but the trunk of the body typically will stay upright or in a more forward position than that of a bilateral feet-forward slip and fall. Environmental factors to be considered are the coefficient of friction of the floor surface, contaminants on the surface, presence of warnings and/or mats, etc.
Another example of a fall on properties can include missteps (e.g., at a single riser change in elevation, stairs, etc.). Commonly considered environmental factors include the presence of handrails, warnings, conspicuous markings on nosings, etc.
While each type of fall has unique considerations from the perspective of environmental features, the human aspects of these incidents share commonalities. These include gait pattern, clothing (e.g., footwear), physical health, expectations, etc. Examination of the human-environment interaction in the context of slips, trips, and falls will include whether features of the walking surface and/or obstacle(s) are readily perceivable and avoidable to a reasonably attentive pedestrian within the context of the general incident area.
A common element in assessing the perceivability of a walkway hazard is available lighting at the time of the incident. The presence of artificial illumination along walking surfaces is particularly important to consider when little to no ambient illumination is present. While people often mistakenly believe they can safely navigate darkened environments, visual processing of objects and fine details are degraded under these conditions. Therefore, illuminance measurements under conditions comparable to an incident can be a key element in the analysis of a fall.
Transportation
While analyses of traffic crashes often include engineers specializing in accident reconstruction, human factors professionals can offer additional, unique insights into the perception and response of typical drivers. Specifically, a human factors expert can apply their expertise regarding human capabilities and limitations (i.e., perception and cognition) to assess the “reasonableness” of a driver’s response to a hazard.
In assessing a driver’s response to a hazard, it is important to distinguish between the visibility and conspicuity of objects. Visibility describes a driver’s ability to detect an object when they are aware of its location. Conspicuity refers to properties of an object in the context of its environmental surroundings, such that the object can capture the attention of a driver whose attention may be directed elsewhere. Addressing the adequacy of an object’s conspicuity is often a factor in collisions involving pedestrians, bicyclists, commercial vehicles, and objects in/along the roadway.
Environmental factors to consider in assessing the conspicuity of a hazard, and whether it is perceivable, can include ambient lighting, properties of the hazard (e.g., color, presence of retroreflective elements, luminance), surrounding landscape, etc. Drivers’ expectations under the conditions and circumstances of a collision are often an essential consideration in analyzing their interpretation of available visual information. Additional driver characteristics to consider include attention/distraction, impairment, visual health, etc. Conducting a human factors analysis to determine the conspicuity and perceivability of a hazard can allow attorneys, judges, and/or juries to better understand the likelihood that a collision could have been avoided.
A common question to evaluate the likelihood of a collision occurring is whether a driver should have perceived and responded to some hazard with enough time to avoid impact. The perception response time (PRT) interval typically starts when a potential risk is first detectable, (i.e., something appearing to move towards or into the driver’s path) and ends when the driver initiates a response. In order to analyze data related to a driver’s response to a hazard, it is important to consider the context in which the incident occurred. Therefore, reliance on a single PRT value without consideration for any factors that may affect a driver’s perception and performance is inappropriate and oversimplifies the complexity of driving. A human factors expert relies upon applicable literature and research to provide a framework to understand a driver’s response (or lack thereof).
Conclusion
While other experts can offer insight into specific issues related to the environment or human for matters in civil litigation, a human factors professional can address the complexity of the interaction between the two as well as their individual contributions.
At Perceptio Forensics, we provide human factors consulting services in a variety of practice areas, aiming to provide our clients with objective, evidence-based insight into their cases. Interested in learning more about human factors and its applications? Feel free to reach out to either Dr. Hartman or Dr. Whetsel Borzendowski.
