Heinrich (1959) is credited with documenting the first scientific method of injury prevention and the effects of accidental injury causation. It is reported that his studies involved 75,000 insurance accident report cases of the 1930 era. His study produced figures to indicate that 88% of the investigated accidents were caused by unsafe acts, 10% due to unsafe conditions and 2% as unpreventable.
Heinrich suggests that in the majority of cases the workers individual characteristics and behaviour are the root cause to most accidents. An individuals personal traits or mindsets being either inherited or acquired will predispose them to increased risk taking ie. recklessness, stubbornness, avariciousness, etc., and predisposes a concept of subjective judgment.
Heinrich demonstrated his theory similar to five dominoes placed end-on-end. Knocking over one creates each domino to topple in turn:
(2) social environment,
(3) fault of person /unsafe act or condition,
(4) accident and,
Heinrich hypothesised that factors in an injury-accident could be altered by removing one thus breaking the knock-down sequence. Essentially to prevent ‘loss’, remove the unsafe act or the unsafe condition. Taylor (2001)
Relative to the task, judgement by management must be made to a persons’ skill level to undertake the task, the provision and understanding of the rules and procedures in order to perform the task, and the supply of general information to the functions surrounding task/s. Attention should altogether focus on human errors as Heinrich apportioned a 10% factor to unsafe place / conditions whereas 88% is unsafe acts.
Modifying or removing the unsafe persons attitude, management can change the characteristics and encourage such workers to be safe. Safety behaviour modification programs (as opposed to attitude programs) would be directly lead by personnel concerned with worker safety, commencing with immediate supervisors with demonstrated support from senior line managers through initiatives such as policy implementation.
Thereby Heinrich theorised that accident / injury cause can be reduced by modifying human error, given the basis that some worker traits are careless or carefree. The critical summation is that the actors have the ability to choose between safe and unsafe acts or behaviour and management has the ability to identify the types of human characteristics and developed work systems and procedures to accommodate them all.
Energy Damage Model is a problematic engineering approach that essentially requires the workplace to identify all the various types and forms of potentially harmful energy sources and controls such loss by designing away the problem that in all probability may present a problem for the actor. While the energy itself may not necessarily be a danger, the problem arises when an unwanted and harmful energy source is transferred unexpectedly (in type, time, speed or force) on to unwilling or unwitting person/s.
Largely the countermeasures of the energy damage model, has characteristics identified in Heinrich’s ‘unsafe person’ theory with the focus on the elimination / reduction at the source in order to control unplanned occurrence/s. Viner’s (1991) energy damage model also places the focus of attention at the pre-event energy control stage to reduce, prevent, modify, separate, etc., before the loss of control causes the harmful energy across to a person and asset. Given ‘man and machine and/or energy’ co-exist and do not act separately, engineering solutions should be designed to relieve cognitive human weakness. Gibson (1961)
Viner’s theory suggests the identification and control of potentially harmful energy eliminates or reduces the latent conditions of the unsafe person while operating in an unsafe place.
Unlike Heinrich and Viner’s scientific approaches to control safety outcomes, Reason’s ‘Swiss cheese’ method is non-scientific and theorises a holistic organisational approach that facilitates human error but more as a consequence than a cause. Reason (2001)
Reason suggests that even in a highly sophisticated and well maintained workplace if relatively obscure shields (defences) are weakened, say through a lack of review following upstream change, several of these components will align to permit accidents to occur, thus becoming an unsafe place.
Time and inattention create these latent conditions and may occur despite a highly skilled and motivated workforce. Managers who oversee highly trained workers become perplexed when workers make active failures, errors, particularly in situations of high quality workplace environments. Top down management approach to accident investigation should consider strategic decisions which shape an organisation which may influence resource distribution to form part of the accident fabric.
Rasmussen (1990) classifies human behaviour into three classifications (errors and faults) being, Skill based slips / lapses, Rule based mistakes and Knowledge based mistakes upon the individual worker and their performance relative to the demands of the task. Classifying worker type, for example, despite the rules to the contrary a worker routinely takes a shortcut knowing such violations go unpunished. This behaviour becomes a normal way of work somewhat automatic and unconscious. Which rule rules ?
Rule reliance for controlling different situations and operator competency levels must be well thought through for explicitness in their given situational variety. The less competent the operator the less abstract the rule must be.
Rasmussen (2002) expanded the above underlying theory has been expanded beyond the local or immediate workplace focus in traditional risk analysis, to take in external psychological impacts of government, subordinate authorities, politics, public opinion and the market place in general. Identified as Acci-Map, this method draws in external factors which form part of management decision making processes, which in turn are transferred to lower workplace levels. For example managements’ compliance duties with regulatory ‘constraints’ coupled the business performance pressures ‘survival’ caused by competition. Perhaps unwittingly, perhaps not, line managers transfer these pressures down to all levels of the workplace where the consequence of errors tend to be focused.
Difford (2011) sets out to debunk what he considers to be some erroneous assumptions and theories in modern risk management. Reason gets a particularly critical treatment and Difford basically tries to dismantle the entire Swiss Cheese Model and related subjects, including the term organisational accident which in Difford’s opinion is a myth because the search for management failures would turn any individual accident into an organisational accident. Other themes are barriers and systems and ‘latent conditions’ and whether these are causes or not, stop rules versus Reason’s and Hollnagel’s continuously “taking things one step further back” and the danger of jumping to conclusions by defaulting to management factors. (for a more thourough review of Diffords new book please review Carsten Buschs review at http://heach.blogspot.com/search/label/Difford)
In risk analysis there is a place Identifying characteristics that influence risk perception and acceptance including involuntary exposure, lack of personal understanding over outcomes, uncertainty of probabilities and consequences, lack of personal experience with the risk, difficulty in imagining risk exposure, effects of exposure delayed in time, consequence and benefits not highly visible and accidents caused by human failure rather than natural causes.
Unfortunately many workplaces have a tendency to apportion blame on the worker in near-miss or accident situations. Not unsurprising this is a natural human trait to avoid self criticism and look for fault in others in a process, particularly by those in positions of authority or those having ‘expertise’ in their field.
Such a worker focus possibly distracts from real causation in accident investigation and more importantly elimination of incidence reoccurrence.
It is suggested that no single accident prevention model discussed could facilitate total elimination of incident reoccurrence due to the variety of pathways unwanted energy damaging sources impact on an organisation. Nevertheless it would be naïve, possibly dangerous, to implement a safety control system that categorises a workers psyche in isolation.
Heinrich’s safety focus is via five chronological factors:- human ancestry, social development, human fault / physical and mechanical hazard leading to accident and leading to possible injury. The focus on the ‘unsafe person’ or unsafe act to be the mostly likely cause of an accident appears somewhat flawed as it assumes the worker has power to change his workplace environment.
Heinrich’s model places a significant assumption the workplace is a relative safeplace and rectification to a given safety issue or accident prevention, largely requires simply encouragement to adjust or readjust worker attitude for those responsible for rule breaches to management or organisational rules.
Under Heinrich, such focus and attention is largely reactive and promotes modification to worker attitude in order to obtain compliance with workplace procedures and processes in order to achieve safety improvement. Accident investigators would be unduly influenced or at best limited in their search for cause and subsequent outcomes in a culture of worker blame. Almost in total disregard for ill-designed plant workers, safety committees and safety managers only need to apply disciplinary measures and implement, reintroduce, educational programmes typically following an incident.
It is questionable whether ‘education’ programmes achieve sustainable behavioural change (compliance) of the ‘identified’ person held responsible for some front line breach. The individual may not be aware he/she was the cause and such an approach to safety control is one of blame / issue and is reactive, therefore in isolation it is narrow in approach and application.
Reason’s holistic organisational approach considers human error more as a consequence than a cause. Questioning those actors psychology at the centre of an investigation could be but a small element in the equation, however other organisational issues must be considered central to the consequence / outcomes.
Rules based models have several drawbacks, first is that every conceivable situation must be identified and applied as well as overseen by a significant supervisory presence to ensure straying is discouraged. Naturally given the frailties of human behaviour and not all possible events can be identified, in advance, accidents and injury would most likely remain.
Viner (1991) suggests hazards are sources of potentially damaging energy, requiring its identification and control of unwanted energies. The loss of energy control becomes the event which is the centre sequence of the incident, not the commencement. Rather than human focus the investigators attention is on engineering-out unwanted energy release and the commencement point for accident and risk analysis. Controlling the unwanted energy excludes harm to the human.
The main investigation focus becomes the time sequentially occurring pre-event in which various energy forms are required to produce injury and damage. This time-window could be in terms of years. For example poorly designed equipment for human use.
Viner’s energy-damage model defines terms in non-judgemental ways, away from the focus on people, and towards the identification of energy sources in a progression of limitations: prevention, reduction, release, modification, distribution and separation.
Understanding the benefits of each model could be beneficial in different circumstances and no single model appears to suit all possible applications.
Time is the link between active failures and latent conditions (Reason 2001) although similar to Rasmussen and Viner levels significant accountability it’s the ‘organisational’ level particularly with management, having a very direct responsibility to allocate resources and control, either from worker education (Heinrich), engineering design solution (Viner) or senior level resource allocation (Reason).
Possibly industries with low or limited capital expenditure, low technology, largely ethnic population and so on, may find it desirable to apportion blame upon the worker (active failure / unsafe person) to divert attention away from senior management level. The fear factor may have motivational impacts which benefit a production focus rather than in genuine safety outcomes.
Difford proves one thing irrevocably in his book (Difford 2011). One of the biggest issues risk managers and industry as a whole has to undertake is a clear process of definition of what is a cause, what is a condition, what is a risk and what is a hazard. Difford also goes further to identify the issue of absolutes and experience shows that where risk is concerned, there can be no such premise as absolutes.