Which term describes the classification of information in the perceptual process?

Definition

The Human Factors Analysis and Classification System (HFACS) was developed by Dr Scott Shappell and Dr Doug Wiegmann. It is a broad human error framework that was originally used by the US Air Force to investigate and analyse human factors aspects of aviation. HFACS is heavily based upon James Reason's Swiss cheese model (Reason 1990). The HFACS framework provides a tool to assist in the investigation process and target training and prevention efforts. Investigators are able to systematically identify active and latent failures within an organisation that culminated in an accident. The goal of HFACS is not to attribute blame; it is to understand the underlying causal factors that lead to an accident.

The HFACS Framework

The HFACS framework (Figure 1) describes human error at each of four levels of failure:

1. Unsafe acts of operators (e.g., aircrew),
2. Preconditions for unsafe acts,
3. Unsafe supervision, and
4. Organisational influences.

Within each level of HFACS, causal categories were developed that identify the active and latent failures that occur. In theory, at least one failure will occur at each level leading to an adverse event. If at any time leading up to the adverse event, one of the failures is corrected, the adverse event will be prevented.

Figure 1: The HFACS framework

HFACS Level 1: Unsafe Acts

The Unsafe Acts level is divided into two categories - errors and violations - and these two categories 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 which 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., fail to prioritise attention, checklist error, negative habit).
• Decision Errors: Errors which 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 which occur when an operator's sensory input is degraded and a decision is made based upon faulty information.

Violations

• Routine Violations: Violations which are a habitual action on the part of the operator and are tolerated by the governing authority.
• Exceptional Violations: Violations which are an isolated departure from 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 practices, conditions and actions of individual and which result in human error or an unsafe situation. Condition of operators refers to the adverse mental state, adverse 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 practices, conditions or actions of individuals, and result in human error or an unsafe situation.

Environmental Factors

• Physical Environment: Refers to factors that include both 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 a variety of 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, and this affects 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 operation (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: Organisational Influences

The Organisational Influences level is divided into three categories.

• Resource Management: Refers to the organisational-level decision-making regarding the allocation and maintenance of organisational assets (e.g., human resources, monetary/budget resources, equipment/facility recourse).
• Organisational Climate: Refers to the working atmosphere within the organisation (e.g., structure, policies, culture).
• Operational Process: Refers to organisational decisions and rules that govern the everyday activities within an organisation (e.g., operations, procedures, oversight).

Use of HFACS

By using the HFACS framework for accident investigation, organisations are able to identify the breakdowns within the entire system that allowed an accident to occur. HFACS can also be used proactively by analyzing historical events to identify reoccurring trends in human performance and system deficiencies. Both of these methods will allow organisations to identify weak areas and implement targeted, data-driven interventions that will ultimately reduce accident and injury rates.

HFACS provides a structure to review and analyze historical accident and safety data. By breaking down the human contribution to performance, it enables the analyst to identify the underlying factors that are associated with an unsafe act. The HFACS framework may also be useful as a tool for guiding future accident investigations in the field and for developing better accident databases, both of which would improve the overall quality and accessibility of human factors accident data. Common trends within an organisation can be derived from comparisons of psychological origins of the unsafe acts, or from the latent conditions that allowed these acts within the organisation. Identifying those common trends supports the identification and prioritization of where intervention is needed within an organisation. By using HFACS, an organisation can identify where hazards have arisen historically and implement procedures to prevent these hazards which will result in improved human performance and decreased accident and injury rates. The US Navy was experiencing a high percentage of aviation accidents associated with human performance issues. Using the HFACS framework, the Navy was able to identify that nearly one-third of all accidents were associated with routine violations. Once this trend was identified, the Navy was able to implement interventions that not only reduced the percentage of accident associated with violations, but sustained this reduction over time.

Application of HFACS

While the first use of the HFACS framework occurred in the US Navy where it originated, the system has spread to a variety of industries and organizations (e.g. mining, construction, rail and healthcare). Over the years, the application reached civil and general aviation. Organizations such as the Federal Aviation Administration (FAA) and National Aeronautics and Space Administration have explored the use of HFACS as a complement to pre-existing systems.

HFACS Taxonomy

The HFACS taxonomy describes four levels within Reason's model and are described below.

HFACS Level 1: Unsafe Acts

The Unsafe Acts level is divided into two categories - errors and violations - and these two categories are then divided into subcategories. Errors are unintentional behaviours, while violations are a willful disregard of the rules and regulations.

Errors

Skill-Based Errors: Errors which occur in the operator’s execution of a routine, highly practiced task relating to procedure, training or proficiency and result in an unsafe a situation (e.g., fail to prioritize attention, checklist error, negative habit).

Decision Errors: Errors which occur when the behaviours 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 which occur when an operator's sensory input is degraded and a decision is made based upon faulty information.

Violations

Routine Violations: Violations which are a habitual action on the part of the operator and are tolerated by the governing authority.

Exceptional Violations: Violations which are an isolated departure from 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 - and these two categories are then divided into subcategories. Environmental factors refer to the physical and technological factors that affect practices, conditions and actions of individual and result in human error or an unsafe situation. Condition of operators refer to the adverse mental state, adverse 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 or TRM and personal readiness factors that affect practices, conditions or actions of individuals, and result in human error or an unsafe situation.

Environmental Factors

Physical Environment: Refers to factors that include both 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 a variety of 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 Limitation: Refers to when an operator lacks the physical or mental capabilities to cope with a situation, and this affects 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 operation (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: Organisational Influences

The Organisational Influences level is divided into three categories.

Resource Management: Refers to the organisational-level decision-making regarding the allocation and maintenance of organisational assets (e.g., human resources, monetary/budget resources, equipment/facility recourse).

Organisational Climate: Refers to the working atmosphere within the organisation (e.g., structure, policies, culture).

Operational Process: Refers to organisational decisions and rules that govern the everyday activities within an organisation (e.g., operations, procedures, oversight).

Related Articles

▼ Human Performance Modelling

Generic Error-Modelling System (GEMS)

Heinrich Pyramid

Human Factors Analysis and Classification System (HFACS)

Human Performance Modelling (HPM)

ICAO SHELL Model

James Reason HF Model

LMQ HF Model

PEAR Model

Further Reading

• Scott A. Shappell (Feb 2000), “The Human Factors Analysis and Classification System–HFACS” DOT/FAA/AM-00/7.
• "The Human Factors Analysis and Classification System (HFACS)," Approach, July - August 2004.
• Human Factors Analysis and Classification System–Maintenance Extension (HFACS-ME) Review of Select NTSB Maintenance Mishaps: An Update by John K. Schmidt, Don Lawson and Robert Figlock. Aeromedical Division, Naval Safety Center, and School of Aviation Safety, Naval Postgraduate School, U.S. Navy, 2003.
• Reason, J.(1990) “Human Error”. Cambridge University Press
• Ford, C., Jack, T., Crisp, V., & Sandusky, R. (1999).”Aviation accident causal analysis. Advances” Aviation Safety Conference Proceedings, (P-343).
• Shappell, S. and Wiegmann, D. (2001). “Applying Reason: The human factors analysis and classification system”. Human Factors and Aerospace Safety, 1, 59-86.
• HFACS Analysis of Military and Civilian Aviation Accidents: A North American Comparison.ISASI,2004
• Wiegmann, D. A., & Shappell, S. A. (2003). A human error approach to aviation accident analysis: The human factors analysis and classification system. Burlington, VT: Ashgate Publishing, Ltd.
• US Department of Defense HFACS
• DOT/FAA/AM-00/7 "The Human Factors Analysis and Classification System - HFACS" - FAA
• Shappell, S., Detwiler, C., Holcomb, K., Boquet, A., Wiegmann, D., (2006). Human Error and Commercial Aviation Accidents: A Comprehensive, Fine-Grained Analysis Using HFACS.

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