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Analyzing controller tasks to define air traffic control system automation requirements
ABSTRACTS a VCR and analyzed for postural changes in different phases with both rakes. The modified rake allowed an upright stance in the pulling phase of the raking action. However, during pushing considerable spinal flexion was necessary using this rake. Using an assumed force of 100 N, a biomechanical analysis was carried out to compare the effect of rakes on spinal stresses. A sensitivity analysis was also done on posturai angles, raking angle and the raking force. A biomechanical analysis showed that the modified rake generated a much lower spinal compression than the conventional rake (0.18-0.44 times) during rake pulling. In rake pushing, on the other hand, the modified rake generated a spinal compression of 3-8 times the conventional rake. The spinal compression was most sensitive to raking angle followed by raking force, hip angle and shoulder angle during raking activity.
23.3.45 (124413) Jenu, F F and Gale, A G An ergonomic assessment of mobile Xray units. In: Contemporary Ergonomics 1991, E J Lovesey (Ed). Taylor & Francis, London, 1991, pp 364-369, 2 refs. Four currently available mobile X-ray units were examined with regard to operator ease of use. Measures on which performance of the equipment was judged included operator comfort, safety, speed with which the equipment could effectively be used, and the health and safety of the operator. Consideration was also given to cognitive aspects of the tasks involved. Three separate approaches to the evaluation were undertaken; questionnaire, participative discussion groups, and user trials. Areas of significant design inadequacy in all mobiles were found. These concerned difficulties with unit manoeuvrability and X-ray tube movement.
23.3.46 (124690) Davis, G N The ergonomics design of the Docklands Light Railway B90 vehicles. In
were successfully employed to improve the manufacturers' original design proposals.
Environment 23.3.47 (124437) Youle, A, Collins, K J, Crockford, G W, Fishman, D S, Parsons, K C, Sykes, J, Longmore, J and Pimbert, SL The thermal environment. Science Reviews Ltd in association with H and H Scientific Consultants Ltd, Leeds, Brit Occupat Hygiene Soc Technical Guide No 8, 1990, 86 pp, 66 refs. The main objective of controlling the thermal environment in relation to humans is to match activities to response in order to optimize health, comfort, safety and performance. A number of factors interact within the thermal environment. Ultimately, it is the individual's physiological responses which indicate whether a particular combination of these factors produces too much heat gain or loss and results in unacceptable physiological, psychological or subjective states. The values providing criteria of unacceptable strain are based upon research that has shown that the physical and psychological performance of an increasing proportion of the population will be less effective as these criteria are exceeded in extreme conditions. This document examines the range of human responses to I~ermal conditions and the means by which environments can be monitored and controlled. The Guide is written for persons who are involved in investigating or assessing thermal environments in the workplace, whether from considerations of comfort or of stress (hot or cold). It is not directed at any specific discipline, as involvement in the thermal environment may arise from many areas, including occupational hygiene, ergonomics, medicine, engineering, biology or management.
System characteristics
Lovesey (Ed). Taylor & Francis, London, 1991, pp 375-380, 1 ref.
23.3.48 (124466) Hix, D and Schuiman, R S Human-computer interface development tools: a methodology for their evaluation. Communications of the ACM, 1991, 34.3, 74-87, 7 refs.
The Docklands Light Railway (DLR) has ordered 70 new vehicles for its fleet. They will carry more passengers than the current vehicles and incur shorter boarding and alighting times in order to accommodate the increasing passenger traffic on the system. This paper describes how applied ergonomics research techniques, including expert appraisal and a larger scale user trial,
A comprehensive checklist-based methodology produces quantifiable criteria for evaluating and comparing human-computer interface development tools along two dimensions: functionality and usability. An empirical evaluation shows that the methodology which is in use in several corporate interface development environments, produces reliable (consistent) results.
Contemporary Ergonomics 1991, E J
216
Work design and organization 23.3.49 (123765) Liou, T S and Wang, M J J Rotating-shift system vs fixed-shift system, lnt J Indust Ergonomics, 1991, 7.1, 63-70, 13 refs. The performances of two different shift-work systems were assessed in a resistor manufacturing company over a period of 13 months. At first, the existing rotating-shift system was evaluated; the yield and productivity were found to be significantly affected by shift and working day factors (P < 0.05). The day shift had the best performance followed by swing and night shift. Both the yield and productivity rose for the first four working days, then declined for the following two days. Subsequently, a new fixedshift system was proposed and the performance was again evaluated. Once again, the shift effect was found to be significant for both productivity and yield. Comparing the differences between the two shift systems, both productivity and yield have shown significant differences in swing and day shift (P < 0.05). For the night shift, performance difference between the rotatingshift and the fixed-shift systems was found at P < 0.1. In summary, the fixed-shift system was found to be superior to the rotating-shift system in many aspects. A few months after implementing the fixed-shift system, the company decided to return to the rotating-shift system due to the high turnovers involved in the night-shift workers. The work shift system design implication is also discussed.
23.3.50 (124700) Phillips, M D and Melville, B E Analyzing controller tasks to define air traffic control system automation requirements. In: Human Error Avoidance Techniques Conf Proc, Soc of Automotive Engineers, Warrendale, Pennsylvania, Publication No P-21M, 1988, pp 37--44, 9 refs. This paper describes a task analysis based methodology developed to support the requirements specification, design and operational suitability evaluation of the next generation air traffic control (ATC) system. A sample ATC scenario is used to show the relationship between task analysis methodology, system-level function allocations and user-system interface (USI) design. Task networks and characterizations based on an aircraftto-airspace conflict situation under two different function allocation schemes are described. Methods of using the
Applied Ergonomics
ABSTRACTS task analysis to guide USI design decisions are presented, along with several candidate USI designs developed using these criteria.
23.3.51 (124510) Meshkati, N Integration of workstation, job and team structure design in complex human-machine systems: a framework. Int J lndust Ergonomics, 1991, 7.2, 111-122, 60 refs. The common causes of failure of complex technological systems (eg, nuclear power and chemical processing plants; modem weapon systems) are analyzed. It is demonstrated that in addition to independent and isolated problems at the individual subsystem levels - workstation (interface), job (task) and team (organizational) structure - there is a serious lack and need for a coherent framework to coordinate these subsystems' formation, as well as their integration, in the context of the total system design. It is proposed and demonstrated that the skill, rule and knowledge (SRK) model, developed by Rasmussen (1983), is a high-potential and powerful conceptual framework that could be utilized for the integration of workstation, job and team (organizational) design in the complex human-machine systems.
23.3.52 (124528) Marras, W S and Lavender, S A The effects of method of use, tool design and roof height on trunk muscle activities during underground scaling bar use. Ergonomics, 1991, 34.2, 221-232, 7 refs. Epidemiologic studies have shown that the scaling bar, a hand tool used in underground mining, is frequently associated with the risk of back injury. An experiment was performed to investigate the effects of method of tool use, mine roof height and tool design upon the activity of six trunk muscles and the ability to exert force with the bar. Roof height and scaling bar design had the largest effects on levels of muscle activation. Striking force did not differ significantly between tool designs. A biomechanical model was used to evaluate the collective effects of the trunk musculature activities upon spine loading. It was found that a significant reduction in predicted spine compression and shear forces can be achieved through the use of a counterbalanced scaling bar. The implications of these results are discussed.
Vol 23 N o 3 J u n e 1992
Health and safety 23.3.53 (123837) Wagenaar, W A Risk evaluation and the causes of accidents. Contemporary Issues in Decision Making, K Borcherding, O I Larichev and D M Messick (Eds). North-Holland, Amsterdam, 1990, pp 254-260, 30 refs. Is misperceived risk or consciously accepted risk a major source of accidents? And will it help to tell people who may be involved in accidents about these risks, so that they will be in a better position to avoid them? From an analysis of studies on driving behaviour, on the use of dangerous products and of accidents at sea, it emerges that most accidents are consequences of routine behaviour, which is preprogrammed to such an extent that it occurs without any consideration of risk. The normative model of human decision making, which assumes an exploration of alternatives and consequences, is not applicable to the actual behaviour of people about to be engaged in accidents. People are running risks, but that does not mean they are aware of these risks, or are consciously taking them. The risks people are running are created higher up in organizations and society, at a level where knowledge-based problem solving occurs. At these levels it can be assumed that exploration or alternatives and consequences take place, and that risks, when realized, may be considered. Therefore the author's answer is: No, people engaged in accidents did not misperceive or consciously accept the risks; Yes, many accidents are the ultimate consequence of decision processes in which risks were wrongly omitted, underestimated or wilfully accepted. The author concludes that risk communication should be aimed, not at those individuals who may cause accidents at the 'shop floor', but at those individuals in organizations and society who take decisions that create the situations in which the routine behaviour of others will appear to be unsafe.
23.3.54 (124599) Cohen, H H and Lin, L J A retrospective case-control study of ladder fall accidents. J Safety Res, 1991, 22.1, 21-30, 7 refs. Epidemiological techniques have become more sophisticated in recent years as applied to investigating major public health issues such as smoking, heart attacks and traffic fatalities. This study demonstrates the value of using an epidemiologic approach for identifying risk factors associated with ladder
fall accidents occurring on the job. The results of structured interviews with workers recently experiencing ladder falls at work were compared with those of control workers in the same company, who were ladder users but had not had a previous ladder fall, through various univariate and multivariate statistical techniques. In all, 123 case and 142 control subjects were compared in over 200 items classified into four categories of variables: (a) personal but nonoccupationally related (eg, personality and life stress factors, risk-taking indicators); (b) personal and occupationally related (eg, job experience, prior on-the-job injuries, job stressors); (c) working condition related (eg, work schedule, work demands), and; (d) ladder-use related (eg, hours worked on ladder, surface on which set up, presence of defective condition). The results confirmed the hypothesis that factors temporally closest to the accident event, (ie, specific ladder use and working condition variables) are stronger predictors of ladder falls than variables further away from the event, namely, individual characteristics. This finding sheds light on the relative value of various types of accident control measures that can be taken since such risk factors are not only the most predictive, but are also those more easily dealt with by companies through various administrative and procedural controls. 23.3.55 (124603) Saiminen, S, Saarela, K L, Sanri, J and Rasanen, T Human factors in severe occupational accidents due to moving parts of machines. In: Contemporary Ergonomics 199l, E J Lovesey (Ed). Taylor & Francis, London, 1991, pp 55--60, 14 refs. The aim of this paper is to examine the effects of human error on occupational accidents due to moving parts of machines. The data consist of 99 severe occupational accidents in Southern Finland. 34 of the victims were injured by cutting and pressing parts of the machines. The results showed that human error played a considerable role in machine accidents. Slips were typical human errors in production tasks, whereas errors in the assessment of danger were typical in repairing tasks. 23.3.56 (124745) Cohen, H H and Lin, L J A scenario analysis of ladder fall accidents. J Safety Res, 1991, 22,1, 31-39, 3 refs. Falls from ladders are second only to stairway falls as the most frequent 217
23.3.45 (124413) Jenu, F F and Gale, A G An ergonomic assessment of mobile Xray units. In: Contemporary Ergonomics 1991, E J Lovesey (Ed). Taylor & Francis, London, 1991, pp 364-369, 2 refs. Four currently available mobile X-ray units were examined with regard to operator ease of use. Measures on which performance of the equipment was judged included operator comfort, safety, speed with which the equipment could effectively be used, and the health and safety of the operator. Consideration was also given to cognitive aspects of the tasks involved. Three separate approaches to the evaluation were undertaken; questionnaire, participative discussion groups, and user trials. Areas of significant design inadequacy in all mobiles were found. These concerned difficulties with unit manoeuvrability and X-ray tube movement.
23.3.46 (124690) Davis, G N The ergonomics design of the Docklands Light Railway B90 vehicles. In
were successfully employed to improve the manufacturers' original design proposals.
Environment 23.3.47 (124437) Youle, A, Collins, K J, Crockford, G W, Fishman, D S, Parsons, K C, Sykes, J, Longmore, J and Pimbert, SL The thermal environment. Science Reviews Ltd in association with H and H Scientific Consultants Ltd, Leeds, Brit Occupat Hygiene Soc Technical Guide No 8, 1990, 86 pp, 66 refs. The main objective of controlling the thermal environment in relation to humans is to match activities to response in order to optimize health, comfort, safety and performance. A number of factors interact within the thermal environment. Ultimately, it is the individual's physiological responses which indicate whether a particular combination of these factors produces too much heat gain or loss and results in unacceptable physiological, psychological or subjective states. The values providing criteria of unacceptable strain are based upon research that has shown that the physical and psychological performance of an increasing proportion of the population will be less effective as these criteria are exceeded in extreme conditions. This document examines the range of human responses to I~ermal conditions and the means by which environments can be monitored and controlled. The Guide is written for persons who are involved in investigating or assessing thermal environments in the workplace, whether from considerations of comfort or of stress (hot or cold). It is not directed at any specific discipline, as involvement in the thermal environment may arise from many areas, including occupational hygiene, ergonomics, medicine, engineering, biology or management.
System characteristics
Lovesey (Ed). Taylor & Francis, London, 1991, pp 375-380, 1 ref.
23.3.48 (124466) Hix, D and Schuiman, R S Human-computer interface development tools: a methodology for their evaluation. Communications of the ACM, 1991, 34.3, 74-87, 7 refs.
The Docklands Light Railway (DLR) has ordered 70 new vehicles for its fleet. They will carry more passengers than the current vehicles and incur shorter boarding and alighting times in order to accommodate the increasing passenger traffic on the system. This paper describes how applied ergonomics research techniques, including expert appraisal and a larger scale user trial,
A comprehensive checklist-based methodology produces quantifiable criteria for evaluating and comparing human-computer interface development tools along two dimensions: functionality and usability. An empirical evaluation shows that the methodology which is in use in several corporate interface development environments, produces reliable (consistent) results.
Contemporary Ergonomics 1991, E J
216
Work design and organization 23.3.49 (123765) Liou, T S and Wang, M J J Rotating-shift system vs fixed-shift system, lnt J Indust Ergonomics, 1991, 7.1, 63-70, 13 refs. The performances of two different shift-work systems were assessed in a resistor manufacturing company over a period of 13 months. At first, the existing rotating-shift system was evaluated; the yield and productivity were found to be significantly affected by shift and working day factors (P < 0.05). The day shift had the best performance followed by swing and night shift. Both the yield and productivity rose for the first four working days, then declined for the following two days. Subsequently, a new fixedshift system was proposed and the performance was again evaluated. Once again, the shift effect was found to be significant for both productivity and yield. Comparing the differences between the two shift systems, both productivity and yield have shown significant differences in swing and day shift (P < 0.05). For the night shift, performance difference between the rotatingshift and the fixed-shift systems was found at P < 0.1. In summary, the fixed-shift system was found to be superior to the rotating-shift system in many aspects. A few months after implementing the fixed-shift system, the company decided to return to the rotating-shift system due to the high turnovers involved in the night-shift workers. The work shift system design implication is also discussed.
23.3.50 (124700) Phillips, M D and Melville, B E Analyzing controller tasks to define air traffic control system automation requirements. In: Human Error Avoidance Techniques Conf Proc, Soc of Automotive Engineers, Warrendale, Pennsylvania, Publication No P-21M, 1988, pp 37--44, 9 refs. This paper describes a task analysis based methodology developed to support the requirements specification, design and operational suitability evaluation of the next generation air traffic control (ATC) system. A sample ATC scenario is used to show the relationship between task analysis methodology, system-level function allocations and user-system interface (USI) design. Task networks and characterizations based on an aircraftto-airspace conflict situation under two different function allocation schemes are described. Methods of using the
Applied Ergonomics
ABSTRACTS task analysis to guide USI design decisions are presented, along with several candidate USI designs developed using these criteria.
23.3.51 (124510) Meshkati, N Integration of workstation, job and team structure design in complex human-machine systems: a framework. Int J lndust Ergonomics, 1991, 7.2, 111-122, 60 refs. The common causes of failure of complex technological systems (eg, nuclear power and chemical processing plants; modem weapon systems) are analyzed. It is demonstrated that in addition to independent and isolated problems at the individual subsystem levels - workstation (interface), job (task) and team (organizational) structure - there is a serious lack and need for a coherent framework to coordinate these subsystems' formation, as well as their integration, in the context of the total system design. It is proposed and demonstrated that the skill, rule and knowledge (SRK) model, developed by Rasmussen (1983), is a high-potential and powerful conceptual framework that could be utilized for the integration of workstation, job and team (organizational) design in the complex human-machine systems.
23.3.52 (124528) Marras, W S and Lavender, S A The effects of method of use, tool design and roof height on trunk muscle activities during underground scaling bar use. Ergonomics, 1991, 34.2, 221-232, 7 refs. Epidemiologic studies have shown that the scaling bar, a hand tool used in underground mining, is frequently associated with the risk of back injury. An experiment was performed to investigate the effects of method of tool use, mine roof height and tool design upon the activity of six trunk muscles and the ability to exert force with the bar. Roof height and scaling bar design had the largest effects on levels of muscle activation. Striking force did not differ significantly between tool designs. A biomechanical model was used to evaluate the collective effects of the trunk musculature activities upon spine loading. It was found that a significant reduction in predicted spine compression and shear forces can be achieved through the use of a counterbalanced scaling bar. The implications of these results are discussed.
Vol 23 N o 3 J u n e 1992
Health and safety 23.3.53 (123837) Wagenaar, W A Risk evaluation and the causes of accidents. Contemporary Issues in Decision Making, K Borcherding, O I Larichev and D M Messick (Eds). North-Holland, Amsterdam, 1990, pp 254-260, 30 refs. Is misperceived risk or consciously accepted risk a major source of accidents? And will it help to tell people who may be involved in accidents about these risks, so that they will be in a better position to avoid them? From an analysis of studies on driving behaviour, on the use of dangerous products and of accidents at sea, it emerges that most accidents are consequences of routine behaviour, which is preprogrammed to such an extent that it occurs without any consideration of risk. The normative model of human decision making, which assumes an exploration of alternatives and consequences, is not applicable to the actual behaviour of people about to be engaged in accidents. People are running risks, but that does not mean they are aware of these risks, or are consciously taking them. The risks people are running are created higher up in organizations and society, at a level where knowledge-based problem solving occurs. At these levels it can be assumed that exploration or alternatives and consequences take place, and that risks, when realized, may be considered. Therefore the author's answer is: No, people engaged in accidents did not misperceive or consciously accept the risks; Yes, many accidents are the ultimate consequence of decision processes in which risks were wrongly omitted, underestimated or wilfully accepted. The author concludes that risk communication should be aimed, not at those individuals who may cause accidents at the 'shop floor', but at those individuals in organizations and society who take decisions that create the situations in which the routine behaviour of others will appear to be unsafe.
23.3.54 (124599) Cohen, H H and Lin, L J A retrospective case-control study of ladder fall accidents. J Safety Res, 1991, 22.1, 21-30, 7 refs. Epidemiological techniques have become more sophisticated in recent years as applied to investigating major public health issues such as smoking, heart attacks and traffic fatalities. This study demonstrates the value of using an epidemiologic approach for identifying risk factors associated with ladder
fall accidents occurring on the job. The results of structured interviews with workers recently experiencing ladder falls at work were compared with those of control workers in the same company, who were ladder users but had not had a previous ladder fall, through various univariate and multivariate statistical techniques. In all, 123 case and 142 control subjects were compared in over 200 items classified into four categories of variables: (a) personal but nonoccupationally related (eg, personality and life stress factors, risk-taking indicators); (b) personal and occupationally related (eg, job experience, prior on-the-job injuries, job stressors); (c) working condition related (eg, work schedule, work demands), and; (d) ladder-use related (eg, hours worked on ladder, surface on which set up, presence of defective condition). The results confirmed the hypothesis that factors temporally closest to the accident event, (ie, specific ladder use and working condition variables) are stronger predictors of ladder falls than variables further away from the event, namely, individual characteristics. This finding sheds light on the relative value of various types of accident control measures that can be taken since such risk factors are not only the most predictive, but are also those more easily dealt with by companies through various administrative and procedural controls. 23.3.55 (124603) Saiminen, S, Saarela, K L, Sanri, J and Rasanen, T Human factors in severe occupational accidents due to moving parts of machines. In: Contemporary Ergonomics 199l, E J Lovesey (Ed). Taylor & Francis, London, 1991, pp 55--60, 14 refs. The aim of this paper is to examine the effects of human error on occupational accidents due to moving parts of machines. The data consist of 99 severe occupational accidents in Southern Finland. 34 of the victims were injured by cutting and pressing parts of the machines. The results showed that human error played a considerable role in machine accidents. Slips were typical human errors in production tasks, whereas errors in the assessment of danger were typical in repairing tasks. 23.3.56 (124745) Cohen, H H and Lin, L J A scenario analysis of ladder fall accidents. J Safety Res, 1991, 22,1, 31-39, 3 refs. Falls from ladders are second only to stairway falls as the most frequent 217