In many crash reconstruction cases, key questions need to be answered involving some aspect of human behavior: reaction times (and delays), perception, visibility, impairment (alcohol, drugs and/or fatigue). A human factor analysis assesses the human role in the crash sequence.
The human operator or pedestrian is the thinking part of a transportation system. The human decisions in this thinking process involve three main purposes:
- To follow a route: The observations, decisions and operations required to go from a trip’s origin to its destination.
- To plan driving strategy: Adjusting departure time, speed, position, and direction of motion; giving signals of intent to turn or slow; making any maneuvers that increase or decrease the likelihood of success in avoiding a hazard.
- To devise driving tactics: Actions taken to avoid a hazardous situation (e.g.: steering, braking, accelerating, etc.) to avoid a mishap. In today’s more advanced vehicles, some evasive tactics may actually be taken by the on-board computer in the vehicle, which may engage evasive tactics without driver input.
To a large extent, how well a person performs these three tasks, especially the last two, determines the risks he or she encounters in their travels. Failure predisposes a traveler to situations in which no evasive tactics can be completely successful in avoiding a mishap.
Potential modifiers for human behavior (human factors) that may have an effect on driver perception, response or strategy may include:
- Fatigue, boredom, irritants
- Emotional upset
- Illness or injury
- Pressure, stress, hurry, preoccupation
- Ingestion or inhalation
- Driving distractions including electronic systems on or within the vehicle (GPS, Cell Phone, vehicle displays/controls, texting, system overloads etc.)
- Passenger interaction
- Sun, wind, wave exposure (issues relating to watercraft and marine incidents)
- Experience and training
- Prosthetic devices