Safety: The cheese stands alone

  • Published
  • By Maj. Sam Manno
  • 908th Safety Office
When an accident occurs, our job in Safety is to get to the root cause, determine the "why", and help implement smart solutions to prevent a reoccurrence. A well-known model used to do this is the "Swiss Cheese" model.

Renowned psychologist James Reason developed this accident causation model to demonstrate how most accidents can be traced to four levels of failure: Organizational Factors; Unsafe supervision; Preconditions; and Unsafe acts.

In the "Swiss Cheese" model, the four levels to prevent accidents are modeled as a series of layers, like slices of Swiss cheese. Each slice is an opportunity to stop an error. The holes in each slice represent weaknesses or failures in each layer of the system. When the holes align, all layers are defeated and the result is an accident or incident.

Unsafe Acts
Working backwards in time from the accident or incident, the first layer depicts those "unsafe acts" that ultimately led to the mishap. This level generates the most investigation, and it is the level where most causal factors are uncovered. After all, it is typically the actions or lack of appropriate actions that are directly linked to the accident.

Latent conditions
What makes the "Swiss cheese" model particularly useful in investigating accidents is that it forces investigators to address latent failures within the causal sequence of events. The latent failures are also "holes," but in different slices of cheese. Latent failures, unlike their active counterparts, may lie dormant or undetected for days, months, years or longer, until one day they adversely affect the unsuspecting person or crew.

Within this concept of latent failures, Reason described three levels of human failure described below.

Preconditions for Unsafe Acts
This level involves conditions such as mental fatigue, poor communication and coordination practices, and frequent interruptions. As an example, if a fatigued member fails to communicate and coordinate their activities, poor decisions are made and errors often result.

Unsafe Supervision
In many instances, the breakdown in good practices can be traced back to instances of unsafe supervision. Errors from lack of sufficient supervision are prone to happen. The lack of quality assurance, support systems, training and availability of qualified personnel can increase the potential for more errors. In a sense, these members were "set up" for failure.

Organizational Factors
In Reason's Model, fallible decisions of upper-level management directly effect supervisory practices, as well as the conditions and actions of their personnel. These latent conditions generally involve issues related to resource and acquisition management, organizational climate, and organizational processes.

Examples of these can include acquisition policies & design practices, unit culture, unit deactivation (or the threat of unit deactivation), organizational training issues, and program management/oversight.

Ultimately, causal factors at all levels must be addressed if any prevention system is going to succeed. One needs to know what these system failures or "holes" are so that they can be detected and corrected before an accident occurs.

Understanding and correcting latent failures is critical in conserving our war fighting capability and protecting our airmen.