1 Instructor: Vincent Duffy, Ph.D. Associate Professor of IE/ABE Lecture 20 – Safety Design Tues. April 10, 2007 IE 486 Work Analysis & Design II

2 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

3 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, 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.

4 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.

5 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

6 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

7 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

8 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

9 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 Rasmussen’s 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

10 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

11 Table 14.3 Hazard Matrix

12 Approaches to Hazard Control Person – eg. ‘Warning’ or ‘training’ These include attempts to change the behavior that may be hazardous Eg. Warning: don’t 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.

13 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.

14 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

15 Bottom up - Considering each failure & analyzing what can lead to it Failure Mode, Effects & Criticality Analysis

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18 QOTD 1. FMECA is a a. bottom up approach to safety analysis b. top down approach c. top down to analysis of work designs that use automation d. all of the above e. none of the above