Re: Repeated cautions: necessary or redundant? (Take II)

[eric -dot- dunn -at- ca -dot- transport -dot- bombardier -dot- com]

On the subject of how things need to be designed, I think I heard a variant of
Geoff's story involving the two buttons.
After converting the machine to use two buttons (far enough apart that they
could not be operated with one hand, elbow/hand, or other shortcut) there was
another injury caused by the machine. The reason? One of the buttons had been
forced in with a toothpick/stick reverting the machine back to one button
operation. The machines were then redesigned and retrofitted with a logic
circuit that looked not for both buttons being depressed, but the action of the
buttons going from released to depressed so that the machine would not operate
unless the buttons were both released and then both pressed.
The moral of the story? Safety is never redundant. People familiar with the
discussions of airport security will also be familiar with the "Swiss cheese"
approach to security. No matter where you slice it, there are holes, but none of
the holes goes all the way through.
Safe equipment design and things like warning in manuals have to be done in the
same manner. Possible holes must be plugged when possible or covered by
alternate safeguards when they cannot.
In the case at hand, I'd argue there should be lights and a siren to warn
surrounding workers of possible danger and no need for the operator to shout
anything. But even then multiple repetitive warnings are required. After all,
sirens and lights may stop working and the operator must be warned to shout if
they are not functional. Remember that the issue here could be life and death.
There are no backups to recover lost data if the operator does something wrong
because they took the procedure for granted and jumped into the manual at a
point that no longer references the warnings, or they take over the procedure
from someone else during a shift change.
Can you really justify it/live with yourself if your removal of a warning for
aesthetic reasons results in the death or dismemberment of a worker? Streamline
the warnings, use pictograms, insert references to other procedures. Anything to
remind the operator of correct safe operation at every chance possible.
For all of those that have a problem with multiple warnings, I'd like to know
what the most danger you've ever put one of your users in or what the nastiest
story you've heard from any of your trainees. My shop teacher in university had
lost fingers to a lathe (I think all the shop guys past a certain seniority had
at least one finger shorter than it should be). More recently the train
operators and mechanics I've trained have told me in detail what happens to
friends and colleagues when proper safety procedures are not followed.
Even more telling is who needs the warnings and cautions. Studies for the safety
department at one of the largest Transit Authorities in North America point to
the fact that the workers most at risk are not the new hires but those with a
few years of experience. They become complacent around danger and forget to
follow an important safety step. So the more ways they can remind workers of
danger the better.

Eric L. Dunn



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