ECE 796896 Human Factor Engineering

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ECE 796/896Human Factor Engineering

• Chapter 20
• Human Error, Accidents, and Safety

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Human Error

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

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Error Classifications

• Discrete Action Classifications
• Errors Of omission, errors of commission,
  sequence errors, and timing errors.
• Information Processing Classifications
• Execution of procedure skill-based behavior,
  rule-based behavior, knowledge-based behavior

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Dealing with Human Error

• Selection Being able to select the correct
  employees for the tasks.
• Training Errors are reduced by proper training.
  Refreshers are good.
• Design
• Exclusion designs, Prevention designs, and
  Fail-Safe designs.

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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.

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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.

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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.

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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

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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 and arousal-alertness

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Cont.

• Psychosocial Goals-freedom-alertness
• If workers are allowed to set reasonably
  attainable goals then good quality performance
  follows. Also when morale is high injuries are
  low.

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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.

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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)

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Special Accident Situations

• Stairs 2 mil injuries, 1000 deaths per year,
  most occur in the home where they rank number 1
  in 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

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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

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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

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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

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Evaluation of Risk

• Ability to estimate risk. This is hard for
• people to do well, usually overestimate low
  risk and underestimate high risk.
• Relative risk People are good at estimating this
  risk type.
• Availability heuristic higher probabilities to
  events they can easily remember. News stories
  bias perceptions of risk.

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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

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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

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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.

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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.

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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.

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Cont.

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

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Effectiveness of Warnings

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

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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.

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Cont.

• 1. Negligence defendant conduct
• 2. Strict liability tests product quality
• 3. Implied warrantee product quality
• 4. Express warrantee or misrepresentation
  product performance vs. manufactures
  representation.

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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.

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When is a Product Defective?

• Patent-Danger rule patently obvious danger -
  later proved poor
• Reasonableness 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.

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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.

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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.