There are two aspects to this framework. Most of the time the multi-layered nature of defences means that if one defence fails another will prevent the hazard from causing damage. However, if there are many holes, a hazard will penetrate. The second aspect of the Reason model is the hierarchy of factors that contribute to defence breaches. The organizational model views human error more as a consequence than as a cause.
Errors are the symptoms that reveal the presence of latent conditions in the system at large.
An effective safety culture will result in few and temporary holes in the defences. A poor safety culture will result in many more holes, as well as holes that remain unaddressed. However, it is difficult to intervene at the level of changing beliefs, attitudes and values. This characteristic is strongly supported by the extensive literature on organisational learning and the knowledge organisation. Good organisational learning.