What Factors Influence Human Reliability?
For practical application, it is important to understand the errors personnel are likely to make. Steps can be taken to eliminate them or, if this is not possible, to minimize the consequences.
The main causes of human error are as follows:
unfamiliarity: a job or situation is important but occurs infrequently or is novel,
time shortage: not enough time is available to complete the job by following procedure or for error detection and correction,
understanding: People do not understand the job properly or no means available to convey information such that it is easy to understand,
“Mental models”: the way the operator imagines a system to work is different to how the designer imagined it,
information overload: simultaneous presentation of information goes beyond a persons capacity to understand,
new techniques: the need to learn new techniques which may follow philosophies opposing those that have been used previously,
feedback system: feedback is poor, ambiguous, or inappropriate,
conformation: no clear conformation is available from the system of the action that is required to control it,
inexperience: the circumstance present requires experience, to understand and control the situation, beyond that of the person involved,
information quality: specified procedures, or instructions from other humans, are of poor quality such that they are inappropriate to the situation present when followed,
diversity: the system has no diversity to allow checking of information presented,
physical ability: the person does not have the physical ability to perform the required tasks,
mental stimulation: the person is required to spend a lot of time either inactive or involved in highly repetitive, menial tasks,
disruption: work patterns cause disruption to normal sleep and rest cycles,
pacing: other people influence the pace at which tasks can be performed,
over manning: more people present than required to do the job satisfactorily.
What Factors Influence Human Variability
Human performance depends on a lot of factors which means they perform differently in different situations. Below are list of factors that affects people performance.
reaction to stress,
fatigue,
supervisor's expectations,
social interaction,
social pressure,
group interaction and identification,
crew efficiency,
morale,
time at work,
idle time, and
repetition of work.
These factors should be taken into account for considering reliable system. What is the possibility that good engineering practice will not be followed? It is also important to consider these factors when selecting personnel or setting up teams.
The Prevention of Human Error
If we eliminate human error or at least reduce the consequences, we will have gone a long way to preventing failures. To improve human reliability, we need to understand what affects it. Human's will always make errors, the reason that failure happen because of latent errors that are present in the systems which do not give the operator a chance. These latent errors are the root cause of most failures. The way to reduce human error through effective management such that reliability is considered important by everyone involved.
Ways to Reduce Human Error
The Procedures
Procedures are very important and should be well thought out.
They should be clear, precise, and easy to read.
They should be easily understood by those who will use them. The best way to achieve this is to write procedures with close participation with those people.
They should be easily accessible.
Checklists should be provided, to be followed for unusual circumstances. The system should be checked for any shortcuts that may be easy to take and that will cause risk.
Audits
These will generally be regular checks made by independent assessors covering a wide range of features like whether maintenance procedures are followed or not, whether equipments are running within operating window or not etc. They provide a good indication of the obvious problem areas.
Increased Discipline
Here people are punished for the failures they are involved in. Once again, this is more likely to reduce reporting of errors rather than necessarily the number of failures. It also requires placing the blame on certain people. Although an operator might have been directly involved, the failure is more likely to have been caused by latent human errors which may not be so obvious and are out of their control. Of course, it is usually the management of a company that would decide who to punish, blaming an operator is a lot easier than blaming a manager who is really more responsible by allowing latent errors to be present in the system.
Increased Automation
Here human manual control is replaced by automatic controls, generally electronic devices. These devices will do as instructed without the problems of human variability and unpredictabilty. With a high amount of automation, the human has different tasks to perform. They are basically there to deal with unforeseen circumstances or to perform tasks that the designer cannot automate. This generally means that during normal operation there is less to be done. Automation can be useful but must be designed correctly. The information should match the operators own mental idea of what is happening. The information should be useful. Important information should be given priority, cross checking should be possible to validate information, alarm analysis and decision aids should be included. Operators probably need more training to operate automated plant although it would appear they have less to do than on a manually operated plant.
Automation can be useful but must be designed correctly. The information should match the operators own mental idea of what is happening. The information
