Slips, Lapses, Mistakes, Errors, and Violations (Reason’s HF model)

People do not err intentionally. Error is a human action that unintentionally departs from expected behavior. Error is behavior without malice or forethought; it is not a result. Human error is provoked by a mismatch between human limitations and environmental conditions at the job site, including inappropriate management and leadership practices and organizational weaknesses that set up the conditions for performance.

SLIPS are errors made when you don’t pay attention or your plan is incorrectly carried out (e.g., you intend to drive to the store but turn the way you usually do to go to work).

LAPSES occur because you fail to carry out an intended action, usually due to a memory failure (you forget to buy something at the store).

Slips and lapses can be classified by type of behavior when it occurs with respect to physical manipulation of facility equipment. The following categories describe how an incorrect or erroneous action can physically manifest itself or ways an action can go wrong:

• timing – too early, too late, omission;
• ƒduration – too long, too short;
• sequence – reversal, repetition, intrusion;
• object – wrong action on the correct object, correct action on the wrong object;
• force – too little or too much force;
• ƒdirection – incorrect direction;
• speed – too fast or too slow; and
• ƒdistance – too far, too short

MISTAKES occur when you plan to do something and carry out your plan accordingly, but it does NOT produce the outcome you wanted (the store does not sell the item you went for). This is often because your knowledge or the rules you applied to decide what to do were inappropriate.

Active Errors

Active errors are observable, physical actions that change equipment, system, or facility state, resulting in immediate undesired consequences. The key characteristic that makes the error active is the immediate unfavorable result to facility equipment and/or personnel. Front-line workers commit most of the active errors because they touch the equipment. Most errors are trivial, resulting in little or no consequence, and may go unnoticed or be easily recovered. However, grievous errors may result in loss of life, major personal injury, or severe consequences to the physical facility, such as equipment damage. Active errors spawn immediate, unwanted consequences.

Latent Errors

Latent errors result in hidden organization-related weaknesses or equipment flaws that lie dormant. Such errors go unnoticed and have no immediate apparent outcome to the facility or personnel. Latent conditions include

• actions,
• directives, and
• decisions

that either create the preconditions for error or fail to prevent, catch, or mitigate the effects of error on the physical facility. 

Latent errors typically manifest themselves as degradations in safeguards, such as weaknesses in processes, inefficiencies, and undesirable changes in values and practices. Latent conditions include design defects, manufacturing defects, maintenance failures, clumsy automation, defective tools, training shortcomings, etc. Managers, supervisors, technical staff, and front-line workers can create latent conditions. Inaccuracies become embedded in paper-based directives, such as procedures, policies, drawings, and design bases documentation.

• Workers unknowingly alter the integrity of physical facility equipment, such as installing an incorrect gasket, mispositioning a valve, hanging a danger tag on the wrong component, or attaching an incorrect label. Usually, there is no immediate feedback that an error has been made.
• Engineers have performed key calculations incorrectly that slipped past subsequent reviews, invalidating the design basis for safety-related equipment.
• Craft personnel has undermined equipment performance by installing a sealing mechanism incorrectly, which is not discovered until the equipment is called upon to perform its function.

The table below summarizes the general characteristics of each kind of error and its immediate unwanted consequences.

As one can see from the table, latent errors are more subtle and threatening than active errors, making the facility more vulnerable to events triggered by occasional active errors.

A study sponsored by the Nuclear Regulatory Commission (NRC) focused on the human contribution to 35 events that occurred over a 6-year period in the nuclear power industry. Of the 270 errors identified in those events, 81% were latent, and 19% were active. The NRC study determined that design and design change errors and maintenance errors were the most significant contributors to latent conditions. The latent conditions or errors often contribute to facility events and cause the greatest increases in risk.

VIOLATIONS involve deliberately (and consciously) departing from known and established rules or procedures (you speed on the way to the store to get there more quickly).

ROUTINE VIOLATIONS—result when a violation becomes what is normally done (the norm) within your workplace, or for you as an individual. Routine violations are often short cuts taken to help you get the job done more quickly, more easily, or perhaps more efficiently. Unless you monitor and control this behavior, it can lead to a culture that tolerates violations.

SITUATIONAL VIOLATIONS—occur when there is a gap between what the rules or procedures require and what you think is available or possible. When there is a lack of local resources, or a failure to understand real working conditions, this may increase pressure on you to ignore procedures or break the rules to get the job done and achieve targets.

EXCEPTIONAL VIOLATIONS—these are one-off actions you might take to deal with an unusual situation, such as speeding to the hospital rather than waiting for an ambulance or jumping into a runaway vehicle to stop it from hitting someone.

Such actions may be either:

1. acts of omission (not doing something that should be done) or
2. commissions (doing something wrong)

Usually, adverse consequences are unintended—violations are rarely acts of sabotage.

The deliberate decision to violate a rule is a motivational or cultural issue. The willingness to violate known rules is generally a function of the accepted practices and values of the immediate work group and its leadership, the individual’s character, or both. In some cases, the individual achieved the desired results wanted by the manager while knowingly violating expectations. Workers, supervisors, managers, engineers, and even executives can be guilty of violations.

Violations are usually adopted for convenience, expedience, or comfort. Events become more likely when someone disregards a safety rule or expectation. A couple of strong situations that tempt a person to do something other than what is expected involve conflicts between goals or the outcome of a previous mistake. The individual typically underestimates the risk, unconsciously assuming he or she will not err, especially in the next few moments. People are generally overconfident about their ability to maintain control.

Examples: When People Commit Violations

Research has found that the following circumstances prompt a person to violate expectations in order of influence.

• ƒlow potential for detection
• absence of authority in the immediate vicinity
• ƒpeer pressure by a team or workgroup
• emulation of role models (according to the individual concerned)
• individual’s perception that he or she possesses the authority to change the standard
• standard is unimportant to management
• unawareness of potential consequences; perceived low risk
• competition with other individuals or workgroups
• interferences or obstacles to achieving the work goal
• conflicting demands or goals forcing the individual to make a choice
• precedent: “We’ve always done it this way” (tacitly acceptable to authority)

The discussion on violations intends to help clarify the differences between the willful, intentional decision to deviate associated with violations and the unintended deviation from expected behavior associated with an error.