Understanding Human Operating Procedures

“People don’t release smoke, grind gears, or have pieces fall off; but their equivalents – fatigue, error, injury, and ill heal
h do result in failure and breakdown."

Martin Moore-Ede, M.D., Ph.D., The Twenty-Four-Hour Society

While our technologies and operations have dramatically changed since the 1993 publication of The Twenty-Four-Hour Society, this statement remains as true as ever.

Why? Because like machinery, we aren’t designed to work outside of our limitations.

Below is an excerpt from The Twenty-Four-Hour Society, written by Martin Moore-Ede, M.D., Ph.D., which details the dangers of operations that are disproportionally machine-centric instead of people-centric.

The discrepancies between these mindsets are foundational to the safety and health of workers and the overall well-being of the operations.

The Twenty-Four-Hour Society: Design Specs of the Human Machine

SOME YEARS AGO I had an opportunity to work with some of the engineers who were designing the crew cabin of the space shuttle. Having been involved with NASA biomedical experiments since the Apollo moon mission days, I was invited to serve on a NASA expert panel advising on human factors considerations for the shuttle. For a young scientist, to work with the best in American engineering – the men and women who had put human beings on the moon – was a thrilling opportunity.

As we looked at several possible crew cabin configurations, my biomedical colleagues and I strongly urged NASA to abandon one scheme, which we felt almost guaranteed that the crew’s blood circulation would be drawn out into the legs during landing, causing unconsciousness. Despite our protests, we were eventually told that the engineers had selected this design.

A year later I learned that the design had subsequently been abandoned in favor of one of the others we preferred. When I expressed delight that the biomedical concerns had finally been acknowledged, I was told the reason for abandoning the previously selected design: undue stress from G-forces would damage the wings. We got the design we wanted, but we had done nothing to alter the mind-set of the engineers!

In most cases of discrimination one group discriminates against another, but here we have a case of discrimination against ourselves.

We treat our man-made machinery better than the bodies of the people who operate it. Machines are protected by operational manuals, warning labels, and training courses. Humans arrive in this world with no such protection. We tend to assume that people are adaptable, but that is true only within narrow limits.

A manager of an industrial plant or a pilot of a plane or a NASA space shuttle, who operated a complex piece of machinery outside of the specifications for which it was designed would be deemed reckless and irresponsible.

Operating a machine out its design specs, at too many rpm, too high a G-force, too high a temperature, or too low a pressure, creates unnecessary risks of breakdown or failure. Yet the most highly sophisticated pieces of machinery in that industrial plant, airplane, or space shuttle are not the complex electronic man-made systems, but rather the bodies and brains of the human operators or pilots.

People believe that machinery is inherently unreliable and must constantly be watched. Yet, with the advances in modern engineering, it is the human operator, more than the machine itself, that needs watching.

We hire people to watch the equipment in our factories, nuclear power plants, and airplanes, but we don’t have the equipment watch the person to ensure that he or she is awake and alert. We have the weak link of the chain watching the strong link, but not the strong watching the weak – the fallible watching the infallible, rather than the infallible watching the fallible.

Because we have been machine-centered in our thinking – focused on the optimization of technology and equipment – rather than human-centered – focused on the optimization of human alertness and performance, the reliability of machines has grown enormously in the twentieth century, while human reliability has tended to decline.

Human error has become the problem of our age because of the trade-offs and compromises, made to ensure the technological achievements of the modern world, have not taken into account the design specs of the human body. Creating and installing a human-centered technology to redress the balance will be one of the most important challenges of the twenty-first century.

The shocking truth is that we know far less about the design specs of the human being than we know about the hardware and software he or she operates. And we tend to abuse those design specs, particularly in around-the-clock operations, which are the core of our twenty-four-hour society.

People don’t release smoke, grind gears, or have pieces fall off; but their equivalents – fatigue, error, injury, and ill health – do result in failure and breakdown.

Source: Martin Moore-Ede, The Twenty-Four Hour Society: Understanding Human Limits in a World That Never Stops, Addison-Wesley 1993.


CIRCADIAN® is the global leader in providing 24/7 workforce performance and safety solutions for businesses that operate around the clock.  Through a unique combination of consulting expertise, research and technology, software tools and informative publications, CIRCADIAN helps organizations with traditional and/or extended operating hours optimize employee performance and reduce the inherent risks and costs of sleep deprivation and fatigue.

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