A5.1 Outline theories/models and use of loss causation techniques Flashcards
What is Heinrich’s Single Cause Domino theory?
according to heinrich:
- a preventable accident is one of five factors in a sequence that results in an injury. The injury is invariably caused by an accident and the accident in turn is always the result of the factor that immediately precedes it.
- the five factors in Heinrichs’s accident sequence are:
- Ancestry and social environment
- Fault of person
- Unsafe act and or mechanical or physical hazard
- Accident
- Injury
Both ancestry and social environment may cause fault of the person which may lead to an unsafe act, and so on.
The major point that heinrich makes is that a preventable injury is the natural culmination of a series of events or circumstances which occur in a fixed logical order. Therefore, the analogy is made to a set of dominos. If one falls, they all fall.
Equally, if you remove one factor, the injury cannot occur and the accident prevented.
What is the systems theory?
This is a way of looking at a multiple-cause situation
Factors and processes can be viewed as systems, components connected together in an organized way to perform a task, with inputs and outputs and various control mechanisms.
System failures are prevented or minimized by components which cannot fail, by backup systems or by redundancy built into the system.
What are the various ways of classifying accident causes?
when analyzing accidents, it is common to distinguish between immediate causes and underlying causes. Underlying causes are sometimes called root causes.
Important to dig down beyond the immediate causes of the accident and look at the result of a multiple chain of events ie. the underlying cause
Immediate cause refers to the direct cause of the accident eg. blade of machine
underlying or root causes are the less obvious, systematic or organizational reasons for the incident.
What is an unsafe act?
What is an unsafe condition?
Unsafe act is human performance which is contrary to accepted safe practice and which may lead to an accident
Unsafe conditions are everything else that is unsafe after you take away unsafe acts.
eg. physical condition of workplace, work equipment, the working environment.
Both an unsafe act and an unsafe condition could independently result in an accident.
What are the concepts behind Reason’s model of accident causation?
- Uses the terms Latent and active failures instead of underlying, immediate, root causes
Reason believed that organizational accidents do not arise from a single cause but from a combination of active and latent failures.
In the model, there a series of defense barriers between the hazard and a major incident. However, the barriers can be defeated.
Active failures are one cause for the barriers to be defeated. These failures are those unsafe acts which have immediate effects on the integrity of the system and are usually committed by those directly involved in the task. The cause of the failure is usually due to an error or a violation.
Additionally, failures at a strategic level with the H&S culture causing accidents are described as latent failures. They are called latent because they remain dormant and possibly unrecognized until they interact with local factors (unsafe acts and work environments) and increase the likelihood of an active failure.
When the gaps created by active failures align with those created by the latent conditions, the opportunity exists for a serious outcome.
What is fault tree analysis? What is Event tree analysis?
FTA is an analytical technique for tracing the events which could contribute to an accident.
The fault tree is a logical diagram based on principle of multi-causality, that traces all branches of events which could contribute to an accident or failure.
It is drawn from the top down. The starting point is the top event (undesired event). Each branch is further developed until a primary failure (root cause) is identified.
ETA is concerned with identifying and evaluating the consequences following the event. The main event in ETA is called the initiating event.
Event trees are used to investigate the consequences of loss-making events in order to find ways of mitigating, rather than preventing, losses.
Stages:
- identifying the initiating event of concern
- identify the controls that are assigned to deal with the event such as safety systems and other factors which may influence the outcome
- construct tree beginning with event and looking at the conditions that may exacerbate or mitigate the outcome
- establish the resulting loss event sequences
- identify the critical failures that need to be dealt with
FTA is concerned with analyzing faults which might lead to an event, whereas ETA considers the possible consequences once an undesired event has taken place.
What is the bowtie model?
Both FTA and ETA can be combined into a bowtie diagram where faults (initiating events) lead to a critical event (flammable gas release)
The critical event then generates consequences which need to be mitigated through the use of barriers designed to prevent catastrophic fire and explosion.
Barriers are either prevention barriers, preventing the initiating event from occurring, or mitigating barriers which minimize the consequence in case of an event.
What is behavioral root cause analysis?
the aim of behavioral root cause analysis is to identify the behaviors that lead to unsafe acts.
Behavioral change programs attempt to change individual worker behavior by positively reinforcing desired behavior and deterring undesired behavior.
Making the safe way of doing something as quick and easy as the unsafe way is a way of improving safety behavior.
Behavioral root cause analysis is an analytical tool designed to examine unsafe acts and establish the underlying unsafe behaviors. It aims to specifically examine the motivations for unsafe behavior to identify the triggers causing the behavior.
