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Warnings. TM 650 – Safety Management Carter J. Kerk , PhD, PE, CSP, CPE Industrial Engineering Department South Dakota School of Mines. Important Issue Concerning Product Use. It may be difficult, impossible, or undesirable to design products that function independently of a human user.
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Warnings TM 650 – Safety Management Carter J. Kerk, PhD, PE, CSP, CPE Industrial Engineering Department South Dakota School of Mines
Important Issue Concerning Product Use • It may be difficult, impossible, or undesirable to design products that function independently of a human user. • The safe and effective use of many products is predominately determined by the decisions and actions people make. • These decisions and actions usually result in safe use, but sometimes mistakes lead to accidents.
Detailed Product Information • Detailed product information can be provided: • intended functions • recommended O&M procedures • product hazards
The Cast Members • Consumers • Employees • Safety Engineers • Manufacturers • Suppliers • Designers • The Courts • Lawyers • The Legislatures • The Insurance Industry
The System • The general process of information transfer must be defined to include a system consisting of: • human • product • task • environment
Warning Definition • Warnings are those stimuli that alert people to hazardous conditions • Such warnings are to be distinguished from operating instructions
Structural Components of a Warning • The Source • high level source of the information • The Channel • with characteristic thresholds, noise levels, and capacities • The Message • as coded information or knowledge • verbal, abstract symbols, pictographs • The Receiver • with characteristics of personality, age, gender, knowledge, education, moods, etc.
Effectiveness of Warnings • Can warnings attract attention? • Exposure to warnings • Filtering of warnings
Stimulus Thresholds • Lower thresholds • must be recognized • Upper thresholds • too strong stimuli can be stressful and interfere with other stimuli • Other issues • nighttime legibility • exit signs in smoky buildings • Cyclops brake lights reduce rear-end collisions • stronger motorcycle lights increase perception
Filtering of Warnings • Humans selectively attend to stimuli • Stimuli compete with other stimuli and noise • What percentage of people receive the warning? • What percentage of people pay attention to the warning after receiving it?
Hammering Experiment • 100 students performed a hammering task • 3 types of warning labels were placed on the hammer • one was supplied by mfg • two others instructed subjects not to use the hammers • 0% followed the instructions not to use the hammer
Wright Experiment • 52 subjects used 60 different consumer products • 34% did not read any instructions
Road Signs • 15 to 30% of motorists did not recall seeing forest fire safety signs • Average recall of last two road signs (within 200 m) for day and night was 4.5% and 16.5% respectively • Users pay more attention to warnings when they perceive greater risk. They will have best recall of road signs they think are most important.
Information Overload • Either too much or too little information may result in poorer decisions • Have you read a drug package insert lately?
Noise Effects • Traffic accidents at a STOP sign increased with the presence of commercial signs (Holahan) • Smoke degraded visibility of exit signs (Lerner & Collins)
Conspicuity Effects • Nonverbal signs can be perceived at greater distances than alphabetical signs (Jacobs) • Auditory stimuli are less easy to filter than visual stimuli (McCormick)
Stimulus too conspicuous? • Aesthetically displeasing (severe color or brightness contrast) may cause consumers to remove labels (Coates) • Disable seat belt buzzer • Danger/Poison symbols (skull & cross-bones) caused containers to be more attractive to young children (42 to 66 months old) (Schneider)
Warning Message Tone Effects • More direct, explicit, or frightening warning labels for lawnmowers were selected as most effective by consumers (McGuinness) • Workers preferred serious to humorous safety posters (Harper & Kalton) • Should not involve horror (shocking, but not lasting), or be negative (shows incorrect behavior) or too general (Sell)
Primary Reference • Warnings, Volume I: Fundamentals, Design and Evaluation Methods; Mark Lehto and James Miller; Fuller Technical Publications, Ann Arbor, MI, 1986