Pearce/Robinson

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IE 486 Work Analysis Design II
Instructor Vincent Duffy, Ph.D. Associate
Professor of IE/ABE Lecture 20 Safety
Design Tues. April 10, 2007
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Safety, Accidents and Human Error

• Ch.14 in Wickens text
• Introduction to Safety and Accident Prevention
• Safety Legislation
• Factors that contribute to accidents
• Human Error Approaches to Hazard Control
• Safety Analysis for Products and Equipment

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Introduction to Safety and Accident Prevention

• Accidents are the leading cause of death of young
  people (under age 44).
• 47000 in motor vehicles
• 13000 from falls
• 7000 from poisoning
• In 1993, 10000 deaths in the workplace alone.
• Overexertion, impact accidents, falls
• Accidents are costly safety is an economic
  issue
• Workplace accidents alone are estimated to cost
  48B per year.

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Safety Legislation

• It is commonly recognized that during the 1800s,
  workers performed under unsafe and unhealthful
  conditions.
• OSHA established in 1970
• Monitors safety in the workplace, however, it is
  understaffed.
• NIOSH National Institute of Occupational Safety
  and Health
• Typically performs research that may later be
  integrated into OSHA standards
• These days, most change with regard to safety is
  due to litigation eg. Product liability
  lawsuits.

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Factors that contribute to accidents

• Task components
• Age younger have more accidents,
• Ability, experience, drugs, alcohol, gender,
  stress
• Alertness, fatigue, motivation, accident
  proneness
• Job
• Arousal, fatigue, physical and mental workload,
  work-rest cycles, shifts, shift rotation, pacing,
  ergonomic hazards, procedures
• Equipment tools
• Controls displays, electrical, mechanical and
  thermal hazards, pressure hazards, toxic
  substances, explosives and other component
  failures

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Factors that contribute to accidents

• Physical Environment
• Illumination, noise, vibration, temperature,
  humidity, airborne pollutants, fire hazards,
  radiation hazards, falls
• Social/psychological environment
• Management practices, social norms, training,
  incentives

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Model of causal factors in occupational injury
Fig 14.1

• Management or design error creating certain
  conditions in the
• Work system
• Includes employee characteristics, job
  characteristics, equipment tools, physical
  environment, social environment
• Natural factors, hazards, operator error
• Leading to accident or injury

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Human error

• Errors of omission
• Leaving out a step
• Errors of commission
• Doing a step incorrectly or adding a step
• Slips
• Intend to step on rung of ladder, but miss
• Intend to save file, but save incorrectly and
  lose it
• How to reduce human error?
• One of three ways
• Selection, training, or system design

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Human error

• It is also important to identify potentials for
  human error
• Some techniques such as THERP
• Technique for human error prediction provide
  guidelines for an analyst to
• identify errors that might occur at each point in
  a task analysis
• Assign probabilities to each error
• Other such methods exist
• Some may suggest the psychological mechanism that
  caused the error, others rely on the
  skills/rules/knowledge based model
• To explain behavior in relation to Rasmussens
  Information processing model.
• So far, none are comprehensive and they tend to
  rely on the ability of the person using the
  method (not very repeatable)
• It is suggested that more than one method be used

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Approaches to Hazard Control

• Risk hazard severity likelihood
• Severity catastrophic, critical, marginal,
  negligible
• Frequency frequent, probable, occasional,
  remote, improbable
• Reducing hazards can be focused on
• Source, path, person, administrative controls
• Source eg. Design out
• Path eg. safeguard
• Keep worker from entering a hazardous area
• Wear protective equipment

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Table 14.3 Hazard Matrix
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Approaches to Hazard Control

• Person eg. Warning or training
• These include attempts to change the behavior
  that may be hazardous
• Eg. Warning dont place hands near pinchpoints
  on machine.
• Administrative eg. legislation
• Other examples include shift rotation, mandatory
  rest breaks, sanctions for incorrect and risky
  behavior
• These are typically not as effective as design
  out (or source solutions).
• How to identify possible methods of hazard
  reduction? read a lot, know/study how people
  will use the product.

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Safety Analysis for Products and Equipment

• Three alternatives
• 1. Designers can consider safety during initial
  design
• Identifying potential hazards of a product, tool
  or piece of equipment when it is first designed.
• 2. Facilities or systems can be evaluated
  proactively to identify hazards to control them
  before accidents occur.
• 3. Facilities and systems can be evaluated in a
  reactive manner by evaluating actual accidents
  to fix the hazards that caused them.

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Safety Analysis for Products and Equipment

• One such method suggests
• Breaking the system or product into
  sub-components
• Then analyzing the sub-components or sub
  assemblies for potential failure
• And then evaluating potential effects of each
  failure
• This the failure mode and effects analysis (FMEA)
• This is sort of bottom-up approach
• A top-down approach could be the fault-tree
  analysis
• From incident or undesirable event to possible
  causes

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Bottom up - Considering each failure analyzing
what can lead to it

• Failure Mode, Effects Criticality Analysis

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QOTD

• 1. FMECA is a a. bottom up approach to safety
  analysisb. top down approach c. top down to
  analysis of work designs that use automationd.
  all of the abovee. none of the above