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Task 1 hed 
Time 
Action 
Emerg 
ence 
Finis 
Improving Human Reliability on 
Checking 
Toru Nakata (AIST, Japan) 
IDHF 20...
About me 
• An expert of IEC TC/SC65A 
– Administrating IEC 61508 “Functional Safety” 
• TC is now discussing expansion of...
Three points to make check more reliable 
1. ‘Staticization’ of workflow 
2. Independent triggering of checks 
3. Objectiv...
1)‘Staticization’ 
• Changing dynamic process to static process 
• Operation becomes safe and easy if you can halt it at 
...
Check under standstill is reliable 
• Counting moving targets is difficult. 
• Static work process allows easy checking 
u...
Standstill at end of work 
6
2) Independent triggering of checks 
• Ordinary “Check after action” scheme is not 
safe. 
7
“Check after action” scheme 
8 
Emerge 
nce Check 
Emerge 
nce Check 
Emerge 
nce Check 
Time 
Action 
Finis 
hed 
Task 1 ...
2) Independent triggering of checks 
• Ordinary “Check after action” scheme is not safe. 
1. The same person undertakes bo...
Independent triggering 
• Check gates should be set. 
– All of workflows should be stopped and checked. 
• Operators can c...
3) Objective Questioning 
Yes/No 
Interrogation 
“Is Toronto the 
capital of 
Canada?” 
Less objective 
(Bad checklists 
c...
Examples for industry 
Yes/No 
Interrogation 
“Have you turned on the 
light?” 
Less 
objectivity 
Question 
without hints...
Conclusion 
1. ‘Staticization’ of workflow 
2. Independent triggering of checks 
3. Objective questioning 
• Those techniq...
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Improve Reliability of Check Tasks

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Check is the most important task of human workers to keep safety. However, ordinary styles of check seem not enough stable. This presentation proposes 3 techniques to improve human reliability of check.

Published in: Engineering
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Improve Reliability of Check Tasks

  1. 1. Task 1 hed Time Action Emerg ence Finis Improving Human Reliability on Checking Toru Nakata (AIST, Japan) IDHF 2014 (Nov. 26, 2014) 1 Task 2 Task 3 Action Emerg ence Finis hed Action Action Emerg ence Finis hed Action Check Check
  2. 2. About me • An expert of IEC TC/SC65A – Administrating IEC 61508 “Functional Safety” • TC is now discussing expansion of 61508 to cover human factors. – How can humans undertake safety critical tasks? • Research Question: How to evaluate/design the reliability of safety-critical systems including human? 2
  3. 3. Three points to make check more reliable 1. ‘Staticization’ of workflow 2. Independent triggering of checks 3. Objective questioning 3
  4. 4. 1)‘Staticization’ • Changing dynamic process to static process • Operation becomes safe and easy if you can halt it at any timing. 4 ‘Dynamic’ Process: The operators have to continue the work unless the beam falls. ‘Static’ Process: The operator can take a break. The supporting pillars make the process static.
  5. 5. Check under standstill is reliable • Counting moving targets is difficult. • Static work process allows easy checking under standstill condition. 5
  6. 6. Standstill at end of work 6
  7. 7. 2) Independent triggering of checks • Ordinary “Check after action” scheme is not safe. 7
  8. 8. “Check after action” scheme 8 Emerge nce Check Emerge nce Check Emerge nce Check Time Action Finis hed Task 1 Task 2 Task 3 Action Finis hed Action Action Finis hed Action
  9. 9. 2) Independent triggering of checks • Ordinary “Check after action” scheme is not safe. 1. The same person undertakes both of action and check for it. – When other workers are busy, the same person have to do both. – Check will be less objective. 2. The worker may omit both of “action” and “check”. – If he forget the action, he also omit the check. – Dependency is the problem. • The trigger of the check is the end of the action. 9
  10. 10. Independent triggering • Check gates should be set. – All of workflows should be stopped and checked. • Operators can check other people’s results. • Resistance against omission. 10 Time Action Emerge nce Finis hed Task 1 Task 2 Task 3 Action Emerge nce Finis hed Action Action Emerge nce Finis hed Action Check Check
  11. 11. 3) Objective Questioning Yes/No Interrogation “Is Toronto the capital of Canada?” Less objective (Bad checklists contain many of those questions.) Question without hints “What is the capital of Canada?” Question requiring rebut “Is New York the capital of Canada, isn’t it?” More objective 11
  12. 12. Examples for industry Yes/No Interrogation “Have you turned on the light?” Less objectivity Question without hints “When did you turn on the light?” Question requiring rebut “Why did you turn on the light?” More objectivity. 12
  13. 13. Conclusion 1. ‘Staticization’ of workflow 2. Independent triggering of checks 3. Objective questioning • Those techniques will improve reliability of humans undertaking critical checking. 13

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