Explaining the Fundamental Contributing Factor Theory Accident Model

No single theory has been developed which can be applied to determine what decision a safety manager must take under all specific risk profiles and all variable circumstance. What is required, being the closest to a theory that tells one which decision to make, are the criteria to be used for decision making. In order to develop appropriate decision making criteria one needs to understand the specific risk profiles, the variable circumstances and the alignment of the maturity levels of the management style with that of the organisation and the skill levels of the work force.

One must establish what the appropriate criteria are for various risk profiles are and then utilize the criteria intelligently. Despite this there can be no guarantee that utilising a set of criteria will result in the correct decision, however it will provide the confidence that the decision maker have the best probability of making the most appropriate decision. One way in which the probability of success can be improved, can be to utilise a scientific model as a basis to formulate decision making criteria.

Most safety decisions are made to prevent accidents or reduce their impact. In order to improve accident prevention decision making criteria it may be beneficial to base these types of decisions on a scientific accident model. It is for this reason that fundamental contributing factor theory accident model is described in this article.

In order to clarify the interaction of the various failure modes present in the model, a graphic representation is represented in a figure that can be accessed by following the link. Graphic.

In the graphic representation the fundamental contributing factors are represented as individual solid plates rotating at individual, varying speeds on a common axis. Each plate in the model represents a fundamental contributing factor associated with a potential accident. The solid parts of the plates represent a perfect condition in each of the elements. The randomly positioned holes in the plates represent failure modes of the fundamental contributing factors. The fundamental contributing factors identified to be present in most accidents are:

• Energy sources out of control,

• Management system failure,

• Training deficiency,

• Latent design defects,

• Inappropriate maintenance,

• Imperfect procedures,

• Unsuitable task directives,

• Substandard physical conditions,

• Unsafe acts,

• Barrier failures.

If at any time all the theoretical holes are aligned, or arranged so that a line of sight passes through all the plates, an accident will result. In practice this means that an unsafe act or any of the other factors alone cannot cause an accident. The unsafe act forms part of a system of interactive failures where all the fundamental contributing factors have a defect lined up in the four-dimensional space-time continuum. This may explain why defects in any of the fundamental contributing factor areas may exist for a long time without an accident resulting.

The following section gives a more in depth description of each of the fundamental contributing factors contained in the model.

Energy Source / Hazardous Materials

According to Haddon (1967) damage is caused to the body of a living being when the amount of energy applied to the body is in excess of the corresponding injury threshold of the body. This implies that when the energy of the impact is greater than the capacity of the body to absorb it, injuries will result. The more the threshold is exceeded the more serious the injury will be. Over the years a significant number of studies have been launched to establish the links between the energy of the impact and the subsequent injuries on the person. Most of these studies have been conducted for and on behalf of the motor industry worldwide. The results of these studies have already significantly influenced design of motor vehicles in the interest of safety.

A number of commonly occurring energy sources have been identified in the literature. For the purposes of the industrial environment the following can be utilized as a guideline:

• Mechanical energy

• Electrical energy

• Thermal energy

• Chemical and Bio-chemical energy

• Electromagnetic energy

• Potential (gravitational) energy

• Kinetic energy

• Acoustic energy

Various elements present prior to an accident may trigger the release of large amounts of energy or hazardous materials. During investigations or preventative design it is important to establish the energy source or hazardous materials that may be causing the injury as a result of the actual or potential exceeding of the threshold limit of the exposed person's body.

Safety Management System Failure

A safety management system is an integral part of the overall management system that specifically facilitates the management of the occupational health and safety risks associated with the business of the organization. This includes the organizational structure, planning activities, responsibilities, practices, procedures, processes and resources for developing, implementing, achieving, reviewing and maintaining the organization's occupational health and safety policy.

The role of safety management system failure should be critically reviewed during the accident investigation. The main objective of safety management systems is to effectively manage the identified significant risks by ensuring that control measures for these risks are constantly in place. This implies that an appropriate risk assessment was conducted and that the resulting risk profiles are utilised to direct prevention activities. As the Safety Management system forms the foundation of the safety management activities it will have to be designed to an appropriate level of complexity to cater for the risk profile of the organization to ensure that it does not contribute to the failure mode and accidents occur as a result.

Training Deficiency

Organizations should have effective procedures to ensure the competence of employees in order to allow the employees to safety carry out their allocated duties. Personnel should be trained to be competent to perform all jobs. The accident prevention training should focus on high risk tasks that could impact on occupational safety in the workplace. To assess the level of competence the employees should be evaluated in terms of their appropriate education, training and/or experience to conduct the high risk tasks.

A lack of appropriate training has been identified by most safety professionals as a major contributor to the unacceptably high accident rate in the industrial environment. To address this problem the industry agreed to the inclusion of various sections in different act that governs industrial safety. A factor that one should be careful about when prescribing training to prevent accidents are that training programmes are normally developed for standard condition and very seldom take cognisance of the varying sub-normal conditions usually present at the time of accidents.

Latent Design Defects

The design of equipment or factory layout and design is recognised as an important factor to ensure that the work environment is inherently safe.

Most existing accident investigation models imply that, in any given situation, latent design defects will affect the likelihood that an accident will occur. Some models call it ergonomics and others construction failure, structural defects or assembly faults. Irrespective of what it is called, most authors agree that latent design defects play an important part in any accident.

Often latent design defects could have been identified prior to purchasing of the parts or equipment but missed as the safety professional does not form part of the approval process for the acquisition of new parts or equipment.

Inappropriate Maintenance

Most modern accident investigation models have underplayed the contribution of inappropriate maintenance to accidents. Vincoli (1993) identifies maintenance as a factor in accidents but focuses on the contribution that maintenance personnel can make in identifying potential hazards and risk.

One (correct) interpretation of maintenance are the replacement of worn components on equipment with suitable components prior to such worn components contribute to an accident happening.

Another view that is just as critical in preventing accidents is that the design, configuration and layout of structures and assemblies be maintained to prevent such deviation to contribute to accidents happening. In practice a number of cases have been recorded where the design or layout are not maintained, it contributed to serious accidents occurring.

Imperfect Procedures

The developing and implementing of appropriate procedures will not in itself result in an accident free work environment, however it is a known fact that where appropriate procedures have been implemented the number of accidents are significantly less than workplaces where this is not the case.

According to Vincoli (1993) procedures should be developed to assist personnel to safely operate hazardous systems. He continues that procedures may include the use of personal protective equipment in hazardous conditions. There are a number of regulatory requirements and Act of parliament that also identifies the use of personal protective equipment as a means of minimising the risk to workers under certain circumstances.

In most instances where the implementation of procedures fails to prevent accidents it has been identified than that the procedure did not take cognisance of variable conditions. In addition to this the buy-in from the workforce to follow a specific procedure is reduced where consultation have not taken place during the development process.

Unsuitable Task Directives

A task directive is a detailed explanation of the steps to be followed to enable a worker to safely conduct the tasks making up a job. In the absence of a task directive the complexities of a task is left to the discretion of the worker. This often, results in tasks being conducted without the impact of the specific order being considered. For this reason all high-risk tasks should be supported with a suitable task directive.

In order to explain the lack of suitable task directives one should consider that the supervisor issuing the task directive normally has a totally different frame of reference than the worker receiving the directive.

The correct way to establish a proper task directive is as follows:

• Put the worker at ease.

• Tell the worker about the task to be performed.

• Explain the context of the task, including the impact it may have on other workers busy on the same job.

• Explain the task detail steps to the worker, emphasising the high risk activities and the standard control measures to reduce the risks of the task.

• Request the worker to repeat the steps of the task, including the safety precautions to be followed.

• Correct any deviations and again confirm understanding.

• Instruct worker when and where to start the task.

The above steps in issuing a task directive is not exhaustive, but is deemed to be the minimum requirement for issuing s task directive.

Substandard Physical Conditions

The physical environment, and especially sudden changes to that environment, should be identified by the worker on the workplace. Changes in the conditions should be dealt with by the workers on discovery. The actual situation at the time of conducting at risk activities is important, not the usual conditions, according to A Guide to Accident Investigation by the Canadian Centre for Occupational Health & Safety to prevent accidents.

Once an accident happened, investigators may want to establish, for example, how the conditions at the time of the accident differed from the so-called normal conditions at the scene in order to establish contributing factors with the aim of preventing future accidents.

It is important that investigators understand that task directives, procedures and maintenance programmes are normally based on so called standard conditions. Should the physical conditions vary from the expected, the task directives, procedures and maintenance programmes may become inappropriate to prevent accidents.

Unsafe Acts

Research about accidents indicates that upwards of 85% of all accidents can be attributed to the so called human factor. The safety manager should not confuse the human factor with unsafe acts. Human factors include behaviours as well as unsafe acts. A full discussion on behaviour is dealt with else ware in this chapter. The unsafe act is the one contributing factor that most authors use to try and explain the reason for accidents, but it is also the most controversial and misunderstood factor. Acts or omissions are often utilised to apportion blame and prosecute individuals under some law. It is normally focused on the acts of the injured or persons in the immediate vicinity of the accident, and in so doing moves the focus away from more remote but equally important unsafe acts.

It is important to try to establish all the so called unsafe acts and or omissions in all the aspects of the at risk activity. Should an unsafe act or mission be identified it must be the aim to prevent such act or omission in the future by understanding the reason for it rather than utilising it to apportion blame for the accident.

Barrier Failure

Barriers consist basically of two types namely physical and time barriers. The purpose of physical barriers is to physically prevent the energy source to come into contact with persons in the event of other failures. When assessing the effectiveness of physical barriers it is important to establish the capability of the barrier to arrest the energy source in such a way that the energy will be dissipated so that the threshold limit of the person potentially in contact with the energy would not be exceeded. Physical barriers include barriers that would absorb the energy of an impact that exceeds the threshold limit of the body. Often such barriers are destroyed during the impact. It is this destruction of the barrier that absorbs the energy and prevents injuries. Such a destruction of a barrier does not means that the barrier failed, as long as the energy level has been reduced to tolerable levels the barrier did the work it was designed to do.

Often it is not possible to install a physical barrier and in these cases a time barrier may be just the answer. A time barrier aims to ensure the absence of persons during a final event. A time barrier is typically the removal of the workforce from the affected area. In a mining environment the workers are normally removed from the mine before the blast is initiated. The workers are then only allowed back once the dangerous gasses have dissipated. A time barrier can only be successfully implemented where appropriate levels of discipline are normal practise in the workforce.

Behaviour

The unpredictability of the fundamental contributing factors aligning in a four dimensional space time continuum can be ascribed to the unpredictability of the behaviour of the various role-players. The fact that very little, if any, attention is paid to the alignment of individual values, with that of corporate safety values, could be the most significant reason for this unpredictability. There are a number of commercially available behaviour intervention techniques that could be utilised to alleviate this problem.

A full description of the concepts and particulars necessary to implement an appropriate behaviour based programme are outside the scope of this article.

Conclusion

Despite the fact that theories and concepts are a very valuable basis in safety management, the practical success lies in the effective translation of these theories and concepts into actions related to the goals and objectives and aligning of the actions with the risk profile.

Theories could be utilised to evaluate past experience and adapt future implementation practises taking these experiences into account. As long as the evaluation takes the variability of the conditions in account a solid analysis is possible.

Irrespective of what accident model is used to investigate accidents it is important to adjust the model dimensions to the site specific risk profile where the accident occurred to gain the maximum benefit from using the model.

© 2009 Carl Marx