|Linear Accident Model||The linear accident model is defined by an accident model, where the relation between cause and outcome is (simplistically) defined linear. This method is best used in systems with a low complexity.|
|Systemic Accident Model||The systemic accident model is defined by an accident model, where multiple relations and correlations are considered and mapped. This model is imperative to understand complex models with multiple factors.|
|Safety I Approach to Safety||The Safety I approach means that the number of things that go wrong (accidents / incidents) is as low as possible. This approach is achieved by first finding and then eliminating or weakening the causes of adverse outcomes, resulting in norms and guidelines.|
|Safety II Approach to Safety||The Safety II approach to safety is defined by a method of ensuring safety in a system, where the aim is to ensure resilience. Understanding that the system is too complex to foresee and mitigate all that might go wrong, the system needs to be engineered in such a way, that the variable factor (human operators) can intervene. Safety is the ability to succeed under varying conditions. Safety II requires an understanding of everyday performance.|
|See: Agenda C.6.3 – WP 155 – Gran Canaria 2014|
In the Systemic model it is assumed that accidents result from unexpected combinations (resonance) of normal performance variability. Failure and success stem from the same source. We change the goal from “avoiding that anything goes wrong” to “ensuring that everything goes right” (TEM, NOSS, LOSA, etc.)
From linear towards systemic:
- It takes teamwork (humans, organizations, technology and society) to succeed as well as it takes teamwork to fail. Air traffic control is not about heroes and anti- heroes
- Safety reporting becomes less relevant to enhance safety
- More emphasis on understanding processes and predicting what goes right
It is time to give systemic safety a more prominent role in ATM, without forgetting where we came from.
IFATCA Policy is:
IFATCA shall adapt to a systemic conception of safety and this shall be embedded in a provisional policy. This means not using new iterations of the linear approach. However, it is recognized that there will be a need for the use of existing linear approach to safety.
|See: WP 165 – Bali 2013|
Last Update: October 2, 2020