2. Accidents. & Errors. Flashcards
(51 cards)
Norman - routine vios
when it is so often it is ignored. ex.: routine shortcuts = vio of procedure
Norman - situational vios
vio under special circumstances. ex.: drive fast because you need to get something
Norman - slips
when someone intends to perform one action, but performs another
Norman - action-based slips
wrong action is performed. ex: put milk in coffee then put coffee cup in fridge instead of milk -> didn’t mean to do that
Norman - memory-lapse slips
intended action is not performed or the results are not evaluated. ex.: forget to turn off gas stove/forget locking door. -> i forgot
Norman - mistakes
wrong goal is set or wrong plan is formed
Norman - rule-based mistakes
good diagnosis of situation, followed wrong rules to base the action. ex.: choosing incorrect procedure/failure to identify risk -> that was the wrong choice
Norman - knowledge based mistakes
wrong diagnosis of problem due to incomplete knowledge. ex.: weighing something in pounds instead of kgs. -> i did not know what i was doing was wrong
Norman - memory-lapse mistakes
when something is forgotten in the goals, plans or evaluation stages. ex.: when mechanic can’t complete everything because he is distracted/skipping step in procedure because you’re doing 2 things at once.
Norman - capture slips
situation where, instead of action, a more frequent action is performed: it records the activity. ex.: leave house and walk to school instead of supermarket
Norman - description similarity slips
error is to respond to an item that is similar to target. ex.: pouring oj in cereal/putting wrong lid on bowl
Norman - memory-lapse slips
immediate cause are interruptions. ex.: forgetting phone/driving with coffee cup on top of the car
Norman - mode-error slip
when a device has different states/modes, causing control to have different meanings. ex.: When an electric guitar is turned off by a switch, if you don’t turn the switch back on, the electric guitar will have a diff sound
Norman - skill-based mistakes
occurs when workers are extremely expert at their jobs, so they can do the everyday routine tasks with little or no thought or conscious attention.
More of a slip
Norman - rule-based mistakes
Diagnose the situation but decide to take the wrong action, (wrong rule is followed)
Eg. go to change your clothes, instead of putting clothes to go out you put on your pj’s
Norman - knowledge-based mistakes
occur when unfamiliar events occur, where neither existing skills nor rules apply.
Eg. weighing of fuel computed in pounds instead of kgs
Norman - memory-lapse mistakes
mistakes due to memory failure to forget goal/plan; due to interruption.
when there is forgetting in-between stages of goals
Disturbe sequence of the action (diff than slips) → happens in higher levels
Norman - design lessons from errors
adding constraints to block errors, undo, confirmation and error messages, make item more prominent, make operation reversible, sensibility checks, minimizing steps
Norman - swiss cheese model
Each slice of cheese represents a condition in the task that needs to be done, an accident can only happen if holes in all the slices of cheese are exactly on the same line. Therefore, it is difficult to look for “the cause” of an accident because it has been preceded by several exactly matching errors. Several ways to reduce accidents are:
- Ensuring more slices of cheese; thus, more defenses;
- Reducing the number of gaps by, for example, better equipment;
- Alerting operators when several holes line up.
Reason - person approach
focus on unsafe acts of people. cause: forgetfulness, inattention, poor motivation etc. just world hypothesis
Reason - system approach
humans are fallible and errors can be expected. error is consequences with origin in systemic factors.
Reason - swiss cheese model
Defenses, barriers, and safeguards occupy a key position in the system approach. o The function is to protect potential victims and assets from local hazards. Most do that effectively, but there are always weaknesses.
• In an ideal world, each defensive layer would be intact. However, they are more like slices of
Swiss cheeses, having many holes. The presence of wholes does not normally cause a bad outcome. Only when the
holes in multiple layers line up at the same time to allow an accident trajectory can
this happen. Active failures = unsafe acts committed by people who are in direct contact with the patient or system.
▪ Direct and short-lived impact on the integrity of defenses.
▪ At Chernobyl, for example, the operators wrongly violated plant procedures
and switched off successive safety systems, thus creating the immediate
trigger for the catastrophic explosion in the core.
▪ Followers of the person approach often look no further for the causes of an adverse event once they have identified these proximal unsafe acts
Latent condition = arise from decisions made by designers, builders procedure writes, and top-level management.
▪ Inevitable resident pathogens (virus) within the system.
▪ May be latent for years within the system before combining with active
failures and local triggers to create an accident opportunity.
• Unlike active failures, which can take a variety of forms that are
difficult to predict, latent circumstances can be detected and corrected before a negative event happens. This knowledge leads to proactive risk management rather than reactive risk management.
• Latent conditions have two kinds of adverse effects:
o They can translate into error provoking conditions within the local workplace; time
pressure, understaffing, inadequate equipment, fatigue, inexperience
o They can create long-lasting holes or weaknesses in the defenses; untrustworthy
alarms and indicators, unworkable procedures design, and construction deficiencies
Reason - error management
Error management has two components:
o Limiting the incidence of dangerous errors;
o Creating systems that are better able to tolerate the occurrence of errors and
contain their damaging effects.
• High-reliability organizations – systems operating in hazardous conditions that have fewer
than their fair share of adverse events – offer important models for what constitutes a resilient system.
o Has intrinsic safety health: is able to withstand its operational dangers and yet still achieve its objective.
Day - goal study
study relationship between level of cognitive failure and individual, psychological stress and workplace accidents
