ECE 796/896 Human Factor Engineering

1. ECE 796/896Human Factor Engineering Chapter 20 Human Error, Accidents, and Safety

2. Human Error • Inappropriate or undesirable human decision or behavior the reduces system performances or causes an accident. • Discrete-action, Information Processing

5. Dealing with Human Error • Selection: • Training: • Design: • Exclusion designs, Prevention designs, and Fail-Safe designs.

6. Accidents • A major objective of Human Factors work is Accident reduction/elimination. • Definition: Unexpected, without cause, mishap … • Indicators: low degree of expectedness, low degree of avoidability, low degree of intention.

7. Human Error and Accidents • Human error is said to cause a large percentage of accidents. • What can be other causes ? • Operator Error or Unsafe Conditions • Blame the active operator, legal system looks at blame/fault, easier to blame the worker than the workplace, forms used point to operator error.

8. Accident Data Analysis • Data Collection: OSHA, MSHA, NSC • Nature of injury, part of body, type of accident, source of the injury • Data bases exist with frequency data, trends • Do not provide data that uncover unsafe situations.

9. Critical Incident Technique • Description of observed unsafe acts or near-miss accidents. • There are more critical Incidents then accidents, there is more data. This data can also show behavior patterns that can be reversed or avoided. • Problems: selective recall and definition of a near miss

10. Accident Causation • Accident Proneness • Some people are more prone to accidents than others, because of some constitutional characteristics. Changes over time (older have lower rates) • Job demand vs. worker capability • Share common ground with accident-liability theories. • Adjustment-to-stress, arousal-alertness

11. Cont. • Psychosocial: Goals-freedom-alertness

12. Factors contributing to Accidents • Contributing Factors in Accident Causation (CFAC): Emphasis on management and social-psychological factors, recognition of the man-machine system by including categories for each component.

13. Study of 248 Accidents • Inadequate SOP: 19% • Error in Recognition: 15% • Error in judgment: 14% • Poor inspection: 12% • Inadequate directives: 10% • Inadequate communications: 10% • Ops error, unskilled Op, other, Maint (20%)

16. Special Accident Situations • Stairs: 2 mil injuries, 1000 deaths per year, most occur in the home where they rank number 1in type of accident. • Most have only one or two steps, poorly illuminated, the steps have no markings and are colored the same as the levels that they connect, handrails not present. • Risers 7-4inch, treads 11 inches

18. Accidental Poisoning of Children • 1980 in 3 months, 28,000 children were treated for ingesting hazardous substances. • 93% happened in the home • 79% child and parent were in different rooms • 89% not closely monitored • 87% parents were engaged in a routine activity • 59% the substance was left out or was in use • 57% the container had a safety cap

19. Reducing Accidents by Altering Behavior • Procedural Checklists: std. In aircraft • Training: stress safe behavior, suitable conditions for practice • Feedback: after training • Contingency reinforcement Strategies: • Behavior modification • Incentive programs:

20. Perception of Risk • Risk,hazard,danger • Hazard: condition or set of circumstances that has the potential for causing injury or death. • Risk: The probability of injury or death • Danger: Risk * Hazard

21. Evaluation of Risk • Ability to estimate risk. • Relative risk • Availability heuristic

22. Risk Perception • Accidents attributed to perceiving risk • Failed to perceive hazard - 36% • Underestimated hazard - 25% • Failed to respond to a hazard - 17% • Responded to hazard, ineffectively - 14%

23. Altering Hazard & Risk Perception • Safety Communications should • Be specific to a particular task and situation • Back up a training program • Give a positive instruction • Be placed close to where the desired action is to take place • Build on existing attitudes and knowledge • Emphasize non-safety aspects

24. Altering Hazard & Risk Perception • Safety Communications should not • Involve horror • Be negative, can show wrong vs right way • Be general, most people will think they act safely.

25. Warnings • Instructions often contain warnings • Approaches to making a product safer • Design the dangerous feature out of the product. • Protect with shielding or guarding • Provide adequate warnings and instructions for proper use and reasonable misuse.

26. More on Warnings • Purposes: 4 principle purposes - 1.Inform the users of a hazard or danger 2.Provide users with information regarding the likelihood of injury 3.Inform users of how to reduce the likelihood of injury 4.Remind users of the danger at the time and place where the danger is most encountered

27. Cont. • Designing: For a warning to change behavior it must be sensed, then received, understood and heeded. • Sensing: Catch the attention, color,size,shape,graphical design, contrast, lights, etc … • Receiving: Levels of warning, Danger,warning, caution • Understanding: Signal word, hazard,consequences, instructions

28. Effectiveness of Warnings • Warnings placed properly in instruction manuals are effective. • Warnings on products - ineffective ?

29. Product Liability • Legal term used to describe an action in which an injured party seeks to recover damages for person injury from a mfg. because the plaintiff believes that the injury resulted from a defective product.

30. Cont. • 1. Negligence • 2. Strict liability • 3. Implied warrantee • 4. Express warrantee/misrepresentation

31. Making a Case • Established that the product was defective in manufacture or design. • When is a product defective. • Product defect is the cause of the injury.

32. When is a Product Defective? • Patent-Danger rule: patently obvious danger • Product is defective if it presents an unreasonable danger to the user. • Failed to perform safely as an ordinary user would expect. • Risks inherent in the design outweighed the benefits of design.

33. Designing a Reasonably Safe Product • 1. Delineate the scope of product uses. • 2. Identify the environments within which the product will be used. • 3. Describe the user population. • 4. Postulate all possible hazards, including estimates of probability of occurrence and seriousness of resulting harm.

34. Cont. • 5. Delineate alternate design features or production techniques, including warnings and instructions, that can be expected to effectively mitigate or eliminate the hazards. • 6. Evaluate such alternatives relative to the expected performance standards of the product, including the following: • A. other hazards • B. subsequent usefulness • C. ultimate cost • D. comparison to similar products • 7. Decide which features to include in the final design.