We have described the main ingredients separately, but in the interviews is often put forward that the programs only work as a whole. This will be explained by Reason’s (Reason, 1995) Swiss Cheese model. The next picture shows the importance of differ- ent barriers at several layers to prevent fatigue within organizations. The so-called ‘cheese model’ shows the importance of defenses in the organization in managing fa- tigue. It is based on Reason’s quote: “we cannot change the human condition, but we can change the conditions under which humans work.”
This is illustrated in the next picture.
Figure 34 The Swiss cheese model (Reason, 2000)
This model has been used as an analogy to describe safety risks. The different layers in the Swiss cheese model reflect the barriers (defenses) a safety system designed to pre- vent errors and therefore, accidents and/or injury. Defensive layers in organizations or
systems can be alarms or physical barriers procedures or preventive action form em- ployees.
Reason’s Swiss Cheese model, (Wikipedia)
The Swiss Cheese model of accident causation is a model used in the risk analysis and risk management of human systems. It likens human systems to multiple slices of Swiss cheese, stacked together, side by side. It was originally propounded by British psychologist James T. Reason in 1990, and has since gained widespread acceptance and use in healthcare, in the aviation safety industry, and in emergency service organizations. It is sometimes called the cumu- lative act effect.
Reason hypothesizes that most accidents can be traced to one or more of four levels of failure: Organizational influences, unsafe supervision, preconditions for unsafe acts, and the unsafe acts themselves. In the Swiss Cheese model, an organization's defenses against failure are modeled as a series of barriers, represented as slices of Swiss cheese. The holes in the cheese slices represent individual weaknesses in individual parts of the system, and are continually varying in size and position in all slices. The system as a whole produces failures when all of the holes in each of the slices momentarily align, permitting (in Reason's words) "a trajectory of accident op- portunity", so that a hazard passes through all of the holes in all of the defenses, leading to a failure.
Mostly these layers achieve this, but there are always weaknesses. This is illustrated by the holes in the slices of Swiss cheese. Unlike cheese, these holes are continually open- ing, shutting, and shifting their location. If the holes in many layers momentarily line up at the same moment, hazards come into contact with victims, an accident occurs. At that moment there will be damaging consequences. Fortunately this will not happen most of the times. The holes in the defenses arise for two reasons: these are active fail- ures and latent conditions.
− Active failures are the unsafe acts committed by people directly related to the in- cident of accident, this can be mistakes or procedural violations.
− Latent conditions are the suboptimal conditions within the system of an organiza- tion.
They arise from decisions made by designers, builders, procedure writers, and top level management. These latent conditions enlarge the chance of potential errors in to the workplace. Examples are time pressure, understaffing, inadequate equipment, fatigue, and inexperience.
These latent conditions may exist within the organization or system for many years before they combine with active failures and trigger an accident opportunity. Unlike active failures, whose specific forms are often hard to foresee, latent conditions can be identified and remedied before an adverse event occurs. Understanding and acting upon this leads to proactive rather than reactive risk management (Reason).
The Swiss Cheese model shows us the importance of multiple measures to prevent risks. Also in the interviews it is mentioned that there is no way to successfully man- age fatigue by using one countermeasure. Success is to be found in a systems ap- proach. It is combination of practices, education, environmental improvements in the workplace and the rest areas. It is important to understand the operational environment where the individual is working and moreover what pressures impact the individual. In the chapter we have described potential measures in a systematic way. The figure below shows the 5 – level model of fatigue management (Dawson & McCullouch,
2005). This model and its levels provide a framework for the multiple measure ap- proach as is reflected earlier by the layers of the Swiss cheese model.
Hazard assessment
Adequate sleep opportunity?
Adquate sleep obtained?
Are there fatigue related behaviours?
Have there been fatigue related errors?
Have there been fatigue related incidents? Error trajectory Level 1 Level 2 Level 3 Level 4 Level 5 = actual incident Control mechanisme - Rules of rostering - Prescriptive rules for hours of work - Modeling (FAID) -Prior sleep wake model
- systems checklist - self reports
- physiological monitoring
- fatigue proofing strategies - SMS adresses 1- 3 level errors in error analysis
- Incident analyses system
Figure 35 the 5 – level model of fatigue management
Dawson and McCulloch (describe a 5-level model, in which each level consists of practical fatigue measures and tools, tools to identify what the risks are, and how to get workload back in balance by redistributing work.
The levels 1 to 3 are aimed at latent errors in the organization (long term, proactive). The levels 4 and 5 are aimed at active errors (short term, reactive and proactive). For example:
− Level 1 consists of tools for rostering and planning of (overtime) works.
− Level 2 consists of tools to identify insufficient sleep, for example sleep loss caused by a sick child during the night, or by attending a party on the weekend. − Level 3 activities are aimed at (self-) reporting fatigue, e.g.: while talking to some
employees in the workplace during a coffee break you observe that one of the staff on your shift is exhibiting symptoms consistent with fatigue. You are aware that this individual has been pushing it pretty hard lately. What do you do? − Level 4 activities reduce risk through “fatigue proofing” countermeasures, e.g.
when somebody has had sufficient sleep, but nevertheless has considerable diffi- culty in staying awake and because you are concerned that there may be a risk of a fatigue-related accident or injury while driving to or from work, you call a cab. − Level 5 consists of incident reporting and analyzing, e.g.: when an incident report
is filed, and the investigation indicates that the employee had reported insufficient sleep prior to the incident
According to this model, there should be measures at several levels to prevent fatigue in order to be effective.