Human error major cause of accidents

A STUDY of the underlying causes of safety incidents in mining has found unintentional human error plays a much bigger role in accidents than is commonly thought. Management system failures or latent errors are at least as significant an issue in generating accidents.
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Roof fall accident

Staff Reporter

The study was commissioned by the Queensland Resources Council to identify the underlying causes of fatalities and significant injury over the past ten years. Over 2000 incidents were analysed to identify six typical, or archetypal, incident types.

Using a range of human error analysis methods, a review was conducted of fatality, serious injury and high potential incident data from Queensland, NSW and Western Australia. The study was conducted by principal research fellows Andrew Morrell and David Cliff of the Minerals Industry Safety and Health Centre (MISHC) at the University of Queensland.

The study found that to reduce incidents with a high potential for fatality or serious injury, health and safety management systems needed to recognise that humans make errors and that in many cases these are not deliberate.

“Current occupational health and safety management systems, risk assessment processes and Job Safety Analyses generally treat humans as machines, behaving totally predictably, consistently, logically and safely. Human errors may not directly cause accidents or injury, but unless corrected or allowed for, these errors can lead to accident or injury,” the study said.

Archetypal incidents (covering 84% of all incidents analysed) were found to be single and multiple vehicle collisions (34%); fall of ground; persons crushed in machinery; persons falling from heights; and persons hit by objects or substances.

Using these archetypes as a base, a further analysis of 109 cases studies was undertaken to identify underlying causes for these incidents.

This analysis showed 57% of errors were human mistakes - the person did not have the necessary ability to do the correct thing at the time, particularly to correct an error of judgement. Cliff said this was contrary to popular belief that errors were made deliberately or carelessly.

Slip/lapses - loss of attention that causes a person to do the incorrect thing (slip) or not to do the correct thing (lapse) - accounted for 17% of human errors. Cultural (routine or tolerated) violations, where people choose to do the incorrect thing because they perceive it to be the expected action by their work group and it is tolerated, occurred overall in 20% of cases studied.

Accidents related to ground falls were dominated by cultural violations. Deviant violations, where people deliberately choose to take incorrect actions even though they know it is not tolerated, only account for 6% of human errors.

For underground coal mines the most significant incident types (in order of importance) are:

· Electrocution – high voltage – trailing cables of shuttle cars etc.

· Single vehicle accidents – due to mechanical failure

· Fire – particularly fires on belts and fixed plant

· Rockfalls/ground control – fall of roof or rib

Though common in coal mines, incidents involving electrocution and fires were not considered in detail because existing controls for these incidents are typically good. Also, low levels of actual injury are associated with these types of accidents.

Overall, the study authors identify three areas requiring major effort from the minerals industry around human error management.

Firstly, operator skills needed to be strengthened to cope with non-normal operations. This might include environmental conditions varying from the “normal”; the change in mining conditions as the mine develops; or approaching loss of control of a hazardous energy.

Secondly, the risk assessment process needed to better identify the need for “Error Forgiveness” in equipment and process operations – that is, equipment should be designed to fail to a safe state. Protection barriers are needed to defend against human error. The researchers suggest behaviour monitoring will reduce human errors or enable specific defences against the acts.

Thirdly, improving site communications and supervision skills will ensure operators have adequate information on changing conditions to adapt their decision-making.

While leadership was not studied directly, researchers underlined its importance. Clear communications and guidance on safe working practices is needed, along with, encouragement of workers to report near misses without fear of punishment; encouragement to work safely (versus productively); encouragement of workers to actively participate in risk assessments and Job Safety Analyses; and the provision of adequate resources for training.