Independence


The need for (and types of) independence in safety-critical systems


Independence is one mechanism used to avoid different types of bias unduly affecting decisions to do with safety, and is often categorised into organisational and intellectual aspects.

  • Intellectual independence is achieved when personnel performing a task have not previously been involved in that task, providing a fresh point of view. For example, a test team comprising personnel not involved in development results in intellectually independent testing.
  • Organisational (or managerial) independence is achieved when personnel are in either a separate part of an organisation or a completely different organisation from any personnel with a vested interest in the outcome of that task, reducing any (intentional or unintentional) pressure. For example, a test team who report to a different manager from the personnel involved in development results in organisationally independent testing.
  • Financial (or commercial) independence is often seen as an extension of organisational independence, requiring that personnel performing a task have no financial interest in the outcome of that task.

AS 61508 "Functional safety of electrical/electronic/programmable electronic safety-related systems" requires an independent safety assessment to be performed by personnel with a level of organisational and intellectual independence depending upon the criticality of the worst credible accidents relating to the system and the Safety Integrity Level (SIL) of the components. Other safety standards have a variety of approaches to ensuring adequate independence.

Why?

A lack of independence in decision-making contributed to the Challenger launch explosion.

Fix?

Savive can provide training to ensure that your organisation has enough intellectually independent personnel, or Savive can provide external consultants to ensure organisational independence.