When good design isn t enough when people really are

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When Good Design Isnt EnoughWHEN PEOPLE REALLY ARE AT FAULTI am sometimes asked whether it is really right to say that peopleare never at fault, that it is always bad design. Thats a sensiblequestion. And yes, of course, sometimes it is the person who isat fault.Even competent people can lose competency if sleep deprived, fatigued,or under the influence of drugs. This is why we have lawsbanning pilots from flying if they have been drinking within somespecified period and why we limit the number of hours they canfly without rest. Most professions that involve the risk of death orinjury have similar regulations about drinking, sleep, and drugs.But everyday jobs do not have these restrictions. Hospitals often requiretheir staff to go without sleep for durations that far exceed thesafety requirements of airlines. Why? Would you be happy having asleep-deprived physician operating on you? Why is sleep deprivation
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considered dangerous in one situation and ignored in another?Some activities have height, age, or strength requirements.Others require considerable skills or technical knowledge: peoplefive: Human Error? No, Bad Design 211not trained or not competent should not be doing them. That iswhy many activities require government-approved training and licensing.Some examples are automobile driving, airplane piloting,and medical practice. All require instructional courses and tests.In aviation, it isnt sufficient to be trained: pilots must also keepin practice by flying some minimum number of hours per month.Drunk driving is still a major cause of automobile accidents: thisis clearly the fault of the drinker. Lack of sleep is another majorculprit in vehicle accidents. But because people occasionally areat fault does not justify the attitude that assumes they are alwaysat fault. The far greater percentage of accidents is the result of poordesign, either of equipment or, as is often the case in industrialaccidents, of the procedures to be followed.As noted in the discussion of deliberate violations earlier in thischapter (page 169), people will sometimes deliberately violateprocedures and rules, perhaps because they cannot get their jobsdone otherwise, perhaps because they believe there are extenuatingcircumstances, and sometimes because they are taking thegamble that the relatively low probability of failure does not applyto them. Unfortunately, if someone does a dangerous activity thatonly results in injury or death one time in a million, that can leadto hundreds of deaths annually across the world, with its 7 billionpeople. One of my favorite examples in aviation is of a pilot who,after experiencing low oil-pressure readings in all three of his engines,stated that it must be an instrument failure because it was aone-in-a-million chance that the readings were true. He was rightin his assessment, but unfortunately, he was the one. In the UnitedStates alone there were roughly 9 million flights in 2012. So, a onein-a-million chance could translate into nine incidents.
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