RCM and the Myths of Human Error

I enjoyed reading Shane Bush’s article, “The Myths of Human Error,” in the July/August 2019 issue of Paper360°. (Read the article here.) Bush points out, “most of the influences on human error come from organizationally-controlled processes—for example, procedures, tools, or communication.”

In my decades of experience, I’ve found that this concept holds up far beyond safety. Since people are involved in every aspect of an organization, then human error can happen in every organizational discipline. This means that every discipline also includes the organizationally-controlled processes that influence error.


Shane points to the concept of “Organizational Weakness”, which he defines as “hidden deficiencies in the organization’s systems, processes, procedures, etc., that lie dormant for some period of time causing no apparent harm until initiated by human action.” He also estimates that organizational weakness makes up 70 percent of the causes for human error. Over my years of working in the maintenance & reliability realm, organizational weakness certainly makes up 70 percent of the causes I have seen, if not much more.


Understanding Error

In Marius Basson’s book Risk-Based Reliability Centered Maintenance (RCM3), human error is broken down into four broad categories:

  • Anthropometric
  • Sensory 
  • Physiological
  • Psychological

I believe that Bush’s concept of organizational weakness is present in all four of these categories, but is particularly dominant in the psychological factors. Psychological error factors can be broken into two types—“unintended actions” and “intended actions”. Unintended Actions are made up of “slips” and “lapses”, while Intended Actions are made up of “mistakes” and “violations”. 

Furthermore, mistakes have two categories of their own: rule-based mistakes, and knowledge-based mistakes. Violations can be broken into three categories: routine violations, exceptional violations, and acts of sabotage. Let’s outline this hierarchy:

A. Unintended Actions – Slips & Lapses

  • Slips are attention failures—something you do incorrectly that you normally do correctly. One example would be wiring a motor backwards.
  • Lapses are memory failures, such as missing a step in a planned sequence of events. An example of a lapse would be leaving a tool inside a pump housing.


B. Intended Actions – Mistakes & Violations

  • Mistakes
    • Rule-based mistakes are when the rule/procedure is followed, but the rule is wrong or not appropriate.
    • Knowledge-based mistakes occur when a new situation arises, there are no rules in place to guide employees, and the reaction is inappropriate.
  • Violations
    • Routine violations are violations that occur frequently and the violation is accepted. An example is when you walk through a plant and see that many folks have their “required” safety glasses on top of their head. Another example is the routine use of a door that is marked “Emergency Exit Only.”
    • Exceptional violations occur infrequently and by exception. One example is when someone who usually wears his safety glasses properly walks into the plant with his safety glasses on top of his head, forgetting to put them on first.
    • Acts of sabotage are occurrences where equipment is maliciously caused to fail. One example is that an “Emergency Exit Only” door, which is supposed to lock automatically when closed, is propped open with a rock. Another example is equipment that is intentionally caused to fail so those working around the equipment can take a bathroom break.

As Shane Bush writes in his article, “Most companies’ investigation processes are traditional fact-based processes, which only communicate what happened, but not why it happened. Context is required to understand the ‘why.’”

Coming to Grips

Marius Basson concludes his book’s section on human error with this statement: “it is only possible to come to grips with human errors if the people involved in committing the errors are involved directly in identifying them and developing appropriate solutions.”


Human error can be controlled, but the reason for its occurrence must be identified. The use of a formal Reliability-Centered Maintenance (RCM) process will identify human error and put actions in place to mitigate its occurrence. RCM is one of the “organizationally-controlled processes” that takes the focus off of “fixing the person” and makes lasting change by improving the process instead.



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