In recent years, a new area of study known as “safety science” has emerged. Safety science is fundamentally connected to several other fields, such as engineering and healthcare. Its scope is not limited to physical and psychological safety, but also includes issues of security, such as cybersecurity. Advancements in safety science aim to inform decision-making in a variety of disciplines.1 One model used by safety scientists to assess risk is the Swiss Cheese Model.
Every slice of Swiss cheese is full of holes. The size and number of holes will vary from one slice to another. In this model, a slice of Swiss cheese is symbolic of a given measure taken to minimize risk. Each slice of cheese can be thought of as a line of defense against accidents. Examples of different “slices” within a given organization may be management, allocation of resources, and an effective safety program.2
Each slice of Swiss cheese has its own unique set of holes. These holes represent shortcomings, or areas where there is potential for failure. Some slices may have more holes than others. When all of a given organization’s slices are stacked together, they represent the organization’s defense against risk as a whole. Since all the pieces of cheese have holes in different areas (which is representative of their differing weak points), sometimes one or more slices of cheese will cover a hole in another slice of cheese. This is symbolic of how some facets of an organization have strengths that can compensate for the shortcomings of others. However, sometimes holes will overlap, resulting in a hole that goes all the way through the stack of cheese. This represents a weak point that is common to all areas of a given organization, where there is the greatest potential for failure to occur.
The Swiss Cheese Model demonstrates how, generally, a failure cannot be traced back to a single root cause; accidents are often the result of a combination of factors.3 It suggests that most accidents are the result of latent errors, which are failures that are intrinsic to a procedure, machine, or system. Latent errors are triggered by active errors, which are unsafe behaviors carried out by individual parties. Thus, it is not simply mistakes made at the individual level that lead to an accident. In models of risk assessment, we must also consider the latent conditions that may be triggered by these errors.4
The Swiss Cheese Model has been used to help organizations understand why accidents occur in spite of their best efforts to prevent them. It is helpful for identifying weak points and for developing strategies to combat them. The goal of safety science is to maximize productivity while minimizing risk of harm, and the Swiss Cheese Model is an asset to the advancement of the field.