The Human Factors Analysis and Classification System (HFACS) was developed by Dr. Scott Shappell and Dr. Doug Wiegmann. It is a human error methodology originally used by the US Air Force to investigate and analyze human factors in aviation. Some of you may recognize HFACS in another form, based on James Reason’s Swiss Cheese model.
The HFACS framework describes human error at each of the four (4) levels of failure:
- Organizational Influences
- Unsafe Supervision
- Preconditions for Unsafe Acts
- Unsafe Acts of Operators
Within each level of HFACS, causal categories were developed that identify the active and latent failures. In theory, at least one (1) failure will occur at EACH LEVEL leading to an adverse event. If at any time leading up to the adverse event, one (1) of the failures is corrected, the adverse event will be PREVENTED.
HFACS Level 1: UNSAFE ACTS
The Unsafe Acts level is divided into two (2) categories – errors and violations– and these are then divided into subcategories.
Errors are unintentional behaviors, while violations are a willful disregard of the rules and regulations.
Errors
- Skill-Based Errors: Errors that occur in the operator’s execution of a routine, highly practiced task relating to procedure, training, or proficiency and result in an unsafe situation (e.g., failure to prioritize attention, checklist error, negative habit).
- Decision Errors: Errors that occur when the behaviors or actions of the operators proceed as intended, yet the chosen plan proves inadequate to achieve the desired end-state and results in an unsafe situation (e.g., exceeded ability, rule-based error, inappropriate procedure).
- Perceptual Errors: Errors occur when an operator’s sensory input is degraded, and a decision is made based upon faulty information.
Violations
- Routine Violations: Violations are habitual actions on the operator’s part and are tolerated by the governing authority.
- Exceptional Violations: Violations that are an isolated departure from an authority, neither typical of the individual nor condoned by management.
HFACS Level 2: PRECONDITIONS FOR UNSAFE ACTS
The Preconditions for Unsafe Acts level is divided into three categories:
- environmental factors,
- condition of operators, and
- personnel factors.
These three categories are further divided into subcategories.
Environmental factors refer to the physical and technological factors that affect individuals’ practices, conditions, and actions and result in human error or an unsafe situation.
Condition of operators refers to the adverse mental state, physiological state, and physical/mental limitations factors that affect practices, conditions, or actions of individuals and result in human error or an unsafe situation.
Personnel factors refer to the crew resource management and personal readiness factors that affect individuals’ practices, conditions, or actions and result in human error or an unsafe situation.
Environmental Factors
- Physical Environment: Refers to factors that include the operational setting (e.g., weather, altitude, terrain) and the ambient environment (e.g., heat, vibration, lighting, toxins).
- Technological Environment: Refers to factors that include various design and automation issues, including the design of equipment and controls, display/interface characteristics, checklist layouts, task factors, and automation.
Condition of Operators
- Adverse Mental State: Refers to factors that include those mental conditions that affect performance (e.g., stress, mental fatigue, motivation).
- Adverse Physiological State: Refers to factors that include those medical or physiological conditions that affect performance (e.g., medical illness, physical fatigue, hypoxia).
- Physical/Mental Limitations: Refers to the circumstance when an operator lacks the physical or mental capabilities to cope with a situation, affecting performance (e.g., visual limitations, insufficient reaction time).
Personnel Factors
- Crew Resource Management: Refers to factors that include communication, coordination, planning, and teamwork issues.
- Personal Readiness: Refers to off-duty activities required to perform optimally on the job, such as adhering to crew rest requirements, alcohol restrictions, and other off-duty mandates.
HFACS Level 3: UNSAFE SUPERVISION
The Unsafe Supervision level is divided into four categories.
- Inadequate Supervision: The role of any supervisor is to provide their staff with the opportunity to succeed, and they must provide guidance, training, leadership, oversight, or incentives to ensure the task is performed safely and efficiently.
- Plan Inappropriate Operation: Refers to those operations that can be acceptable and different during emergencies but unacceptable during normal operations (e.g., risk management, crew pairing, operational tempo).
- Fail to Correct Known Problem: Refers to those instances when deficiencies are known to the supervisor yet are allowed to continue unabated (e.g., report unsafe tendencies, initiate corrective action, correct a safety hazard).
- Supervisory Violation: Refers to those instances when existing rules and regulations are willfully disregarded by supervisors (e.g., enforcement of rules and regulations, authorized unnecessary hazard, inadequate documentation).
HFACS Level 4: ORGANIZATIONAL INFLUENCES
The Organisational Influences level is divided into three categories.
- Resource Management: Refers to the organizational-level decision-making regarding the allocation and maintenance of organizational assets (e.g., human resources, monetary/budget resources, equipment/facility recourse).
- Organizational Climate: Refers to the working atmosphere within the organization (e.g., structure, policies, culture).
- Operational Process: Refers to organizational decisions and rules that govern the everyday activities within an organization (e.g., operations, procedures, oversight).