How can we prevent accidents caused by human error? This presentation deals with typical examples of severe accidents related to human errors, and shows methods to prevent them.

1. Human Error
— Theory and Prevention
Dr. Toru Nakata
National Institute of Advanced Science and
Technology, Japan.
Nov. 20, 2011
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2. Part I
Theory of Human Error Prevention
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3. 1-1
How we make mistakes
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4. Why do we err?
 Unknown
 Even masters of chess sometime commit easy mistakes.
 A lot of typical pattern of “misconception” are found.
 Four-card problem
 Monty Hall problem
 Horse Trading problem
 …
 But there is no universal tendency among them
 Change the question more productive.
 “Why can we usually avoid errors?”
 Because we can notice and fix errors before they break
out.
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5. Horse Trading Problem
 Frank sells Sue a horse for $60.
 Then he decides he wants it back, but Sue makes him
pay $70 for it.
 Then Sue changes her mind and buys it back from
Frank, but for $80 (Frank is no dummy).
 Finally, Frank buys it back from Sue for—you guessed
it—$90 (Sue is no dummy, either).
 At this point, who comes out ahead?
 http://ohiorc.org/for/math/stella/library/problem.aspx?i
d=128
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6. 1-2
Typical Example of Human Error
Accidents
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7. Case 1: Confusing patients
(1999, Japan)
 Patient A: 74 yrs old. Plan to be undergone surgery on
his heart.
 Patient B: 84 yrs old. Plan to be undergone surgery on
his lung.
 Loaded an elevator together,
 Mistaken each other, when they brought out of the
elevator.
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8. But, it was doubtful…
 Some staffs in the operatin room said, “Is he patient A?”
 Different face, vital signs, etc
 Reconfirm by telephone to the patient room
 “Have Patient A been moved to the operation floor?”
 The answer was “yes”
 Yoshida Kenko, a famous author, said in his book “Tsure-
zure-gusa”,
 The top secret skill of horse riding is “do not ride the
horse, when you cannot convince the situation is perfect.”
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9. Case 2: Bhopal accident (1984, India)
 Safeguards are not safe.
 Because, the management for safety becomes reluctant.
 Multiple Safeguards seem highly enough.
 In actual, all safeguard did not work enough.
 Not maintenance for them.
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10. 1-3
What is real meaning of Human
Error?
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11. Don’t say “error”, use term “uncertainty”
 Is “error” wrong? Some errors bring good results at
last. We cannot define “error” as a bad.
 What you are thinking is “uncertainty” in the work
flow.
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12. Three ability for human error prevention
Ability Meaning Power
Detectabilty/ Can you (or work team) Only this ability can prevent
Sensitivity against find hidden mistakes in the accident. Most important
the front of you? ability.
mistakes
Traceability for Can you specify the Greatly reduce the cost to
mistake cause of the mistake? recovery.
Secondary important.
Dexterity Can you do your task Reduce running cost of the
without errors? task. But no grantee for
prevention of accident. (Even
you are OK, other workers
might sow seeds of accidents)
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13. Part 2
Solutions for Human Error Prevention
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14. 2-1
Techniques to ensure human ability
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15. Wake!
 1) Fool-proof
 If the driver sleep, the train will stop automatically
(Fig.1)
 2) Fool-Trap
 If the driver violates speed limit, he will be injured
before he hit somebody else.
15 Fig. 1 Train console Fig.2 Bump of the road.

16. Look your task!
 3) Keep consious about your
task.
 Sing work songs.
Boring line work
 “Cell Production system”
 4) Comfortable weather
 People become thoughless
when it is too hot or cold.
Cell Production
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17. Check with objectiveness
 5) Use body and voice together
 Pointing and Calling
 6) Check by pair
 “Pair programming” in software Check with
production. argument
Check with
reporting number
Yes/No check
Most easy and
unreliable.
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18. This is not end!
7. Prevent sense of achievement at too early timing
Staffs are making a line when their task already finished.
They think they have to keep their tension until this ceremony.
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19. 2-2
Tool and System to prevent human
errors
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20. Zoning
Zoning
No zoning Zoning for sanitary
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21. Metaphor
Remove before flight strap
Tablet representing
representing the mode of door safeguard
right to go forward
Starbucks
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22. Pop-out effect
Which is reverse?
Which is reverse?
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Is somebody there?

23. 2-3
Planning the strategy
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24. Event Tree Analysis (ETA)
Loose file
Mistake
files
Reek files
Mistake
buttons
Mistake Business
Email address stops
Ordinary problem
Other
Other
 Think risk of severe accidents from ordinary problem.
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25. Fault Tree Analysis (FTA)
Iceberg
shipwreck
Collision with other ships
No aids Titanic
Lack of Boats
No rescue
Paticular accident
High sea you have to prevent
 Think the cause of a particular severe accident by
asking why.
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26. How to gather incidents reports easily
When Where What How Reaction Who Review
comment
9-2-Mon- 9:00 Milling Drill Broken Renewal Tanaka OK (Suzuki)
cutter No.3
9-4-Wef- 13:00 Heater Intake Dirty Clean Sato To be
No.5 inspected
(Suzuki）
9-9-Mon- Heater Holder Screw Tight Tanaka OK (Suzuki)
10:03 No.5 loosen
•Easy to write in.
•Bring the data into Excel, and sort them.
•By sorting, you can find which features
(when, where, ….) have got the most reports.
•That are the most dangerous features.
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27. Slogan: “Safety by walking around”
 Hawthorne effect:
 Under the situation that somebody may
watch your working scene, you tend to
perform better, quicker, and safer.
 The watcher is NOT his boss.
 Without duty, people naturally try to
show themselves as good workers.
 Walking around. Meet various staffs
who are not bosses nor subordinates in
order to encourage them. Open Kitchen.
The cook tend to
 Negative Hawthorne effect: perform better and
 Under the situation that your supervisor more
is watching you closely, you fell uneasy moderate, because
27 and tend to refuse the observation. somebody may