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The effect of motorway signals on traffic speed
Description of a case where a worker's inability, through colour vision defect, to see the blue flame from a small hand-held natural gas torch used in soldering work in a car body plant had resulted in his frequently burning himself and his co-workers. The article then traces the development of scientific knowledge of, and research on, colour blindness, with reference to the ILO Encyclopaedia of Occupational Health and Safety, and considers many aspects of colour vision defect (history in early childhood; protan, duteran and trito defects; effects of heredity; race factor; effects of senile cataract; colour vision tests) and job suitability tests (lantern test, etc). 10.2.7(75591) Gallwey, T.J., and Drury, C.G. Size discrimination in visual inspection. In: Human Factors in Transportation, Human Factors in Health Care Delivery. Proceedings of the Tenth Annual Meeting of the Human Factors Association of Canada, September 9 - 1 1 , 1977. An inspection task was broken into its components of visual search and decision-making and these simulated together with the whole task in the laboratory. A computer generated pattern of the digit 8 was used in which the " d e f e c t " was a single digit 3. Eleven heights of 3 were used from 40% smaller than the 8 to 40% larger (including the same size). The experiment was in three parts - in the first subjects had only to find the defect, in the second they had only to decide on the defect size, and in the third these were combined as an inspection task. Times and correct decisions were measured. Median search times were longer for a defect which was smaller than the background and standard compared to one which was larger. Similarly the probability of correct decisions was greater for a 3 smaller than the 8 than for one which was larger. For a probability of correct decisions of at least 0-75 a height difference giving a visual angle of at least 3 ft of arc was required. Crossman's Confusion Function was found to be the measure of discriminability with the best linear fit to both search and decision data.
Auditory processes in man 10.2.8 (76020)
Elliott, L.L. Development of communication aids for the deaf. Human Factors, Jun 1978, 20.3,295-306.
This paper is written primarily for the reader who is not expert in areas of communicative disorders nor actively engaged in research on devices to assit persons with hearing impairments. The intent is to provide a brief introduction and to explain some of the challenges associated with development of sensory aids for the deaf. The discussion also comments on some of the basic human factors questions that deserve attention in the context of improving communication aids.
Information processing and transmission by man 10.2.9 (75635)
Cooper, M.B. The effect of adjacent lamps on the interpretation of a coded flashing lamp. Post Office Research Centre, Martlesham Heath, Ipswich, Post Office Telecommunications Research Department Report No 706, May 1978, I 1 pp. A series of experiments was carried out to investigate the effect of irrelevant adjacent lamps on the speed and accuracy of identifying flashing light codes. In the first experiment, subjects identified the code on a central lamp either in isolation or in a line of three, five or nine lamps. In the second experiment, subjects had to identify the code on a random series of lamps which were specified by means of a numeric display. Subjects in the third experiment searched for a target code on displays of three, five or nine lamps. No effects due to the presence of the adjacent lamps were detected in any of the three experiments. 10.2.10 (75654)
Spitz, G., and Drury, C.G. Inspection of sheet materials - Test of model predictions. Human Factors, Oct 1978, 2 0 . 5 , 5 2 1 - 5 2 8 . The two-stage model of inspection performance suggested in a previous paper was tested in laboratory conditions. Four subjects participated in an experiment to estimate the visual search and decision making components of an inspection task using light circular targets of low contrast on a dark empty field. Predicted and measured performances on the inspection task were compared. It was found that the prediction of independence of component tasks and additivity was upheld. In predicting speed/accuracy trade-off, the model's performance was better
for the high contrast conditions than for the more difficult low contrast conditions.
10.2.11 (76022)
Sinclair, M.A. A collection of modelling approaches for visual inspection in industry. International Journal of Production Research, Jul 1978, 16.4, 2 7 5 - 2 9 2 . The paper outlines the consequences of inspection error for visual statistical quality control schemes and goes on to discuss various approaches that have been adopted to try to estimate the proportion of good items rejected and the proportion of defective items accepted. Brief discussions of these approaches are included, with some criticisms. It is said that most of the approaches used so far have not contributed much towards a model of inspector performance, though there are some recent developments that look a little more encouraging. 10.2.12 (75655) Wade, M.G., and Gold, M.W. Removing some of the limitations of mentally retarded workers by improving job design. Human Factors, Jun 1978, 2 0 . 3 , 3 3 9 - 3 4 8 . The traditionally low level of expectancy of persons with moderate, severe, or profound mental retardation in industrial work settings is reviewed from a human factors viewpoint. A case is made for interfacing the retarded worker into the human machine system b y evaluating performance in terms of information processing ability. Data are reviewed which suggest that there are many industrial tasks at which such a worker can perform well and earn a wage comparable to his non-retarded co-worker. The issue of training workers versus screening workers is discussed as an addtional factor in maximising the role of workers with retardation in industry. The view of the retarded worker as a communication channel and his ability to process information is regarded as a central issue when discussing the optimisation of the person-machine interface. The importance of task analysis in breaking down the task into sub-tasks of acceptable information processing demand is also discussed.
10.2.13 (75657)
Lines, C.J. The effect of motorway signals on traffic speed. Transport and Road Research Laboratory, Crowthorne, Berks. Report No SR-363, 1978, 16 pp.
Applied Ergonomics June 1979
113
The effect on vehicle speed of advisory speed indications shown on motorway signals has been measured at two sites on the M 1 motorway. On an urban section of the motorway at Scratchwood in N London, measurements were made of vehicle speeds before and after a set of signals mounted over the carriageway on a gantry. The signals were set to show an advisory speed of 50 mile/h (80 km/h). Control measurements were also made with the signals switched off. The average speed of light vehicles in the right hand lane was reduced from about 78 to 71 mile/h ( 1 2 5 - 1 1 4 km/h) (9%); in the centre lane from about 69 to 63 mile/h ( 1 1 0 - I 0 1 km/h) (7%%); and in the left-hand lane from about 57 to 55 mile/h ( 9 1 - 8 8 km/h) (4%). Similar measurements were made on a rural section of the motorway at Newport Pagnell where the single signals are mounted on posts in the central reservation. The average speeds of light vehicles in the right-hand lane was reduced from about 77 mile/h to 69% mile/h ( 1 2 3 - 1 1 1 km/h) (91A%); in the centre lane from about 68 to 63 mile/h ( 1 0 9 - 1 0 1 km/h) (7%); and in the left-hand lane from about 55 to 52 mile/h ( 8 8 - 8 3 km/h) (5%). At both sites downstream from the measurement sections, the fast lane was closed for maintenance work. Drivers could not see the temporary signing or the closed lane from the measurement sections, so the speed changes measured would be in response to signal indications.
Factors affecting perceptual-motor performance
system. Thirdly, he may be checking data on the computer against other data he has in non-display form. All of these tasks require concentration on the display screen for long periods of time. The occupational health effects of VDUs derive primarily from the effects of long exposure of the worker to the light, reflection, glare and flickering of the CRT screen. The majority of problems therefore tend to be perceptual and the precipitating causes tend to be multiple and interactive. This report attempts to summarise these and other ergonomic problems of the VDU operator, and provide short, practical recommendations for the installation of VDUs in a clerical environment. A bibliography is provided for further reading. 10.2.15 (75667)
Pepersack, J.P. Human problems arising from the use of microfiches in industry (Problemes Humaine Lies a l'Utilisation des Microfiches dans l'Industrie). (In French.) Cahiers de Medecine du Travail - Cahiers voor arbeidsgeneeskunde, Dec 1977, 14.4, 2 7 9 - 2 8 2 . Abstr in: CIS Abstracts (CIS 78-1480). A typical syndrome is observed in many workers who use microfiche readers: headache, eye fatigue, inflamed conjunctiva, blepharitis, autonomic dystonia, irritability, nervous diathesis, etc. A number of workpost studies revealed several problems: inadequate lighting, difficulty in reading projections, eye strain and nervous strain due to scanning and microfiche, monotonous work, neuropsychic stress. Various solutions are proposed, particularly job rotation. 10.2.16 (75671)
10.2.14 (75665)
Hurst, M.W., and Rose, R.M.
Birnbaum, R.
Objective workload and behavioural response in airport radar control rooms. Ergonomics, Jul 1978, 21.7, 5 5 9 - 5 6 5 .
Health hazards of visual display units with particular reference to office environments. TUC Centenary Institute of Occupational Health, London School of Hygiene and Tropical Medicine, London. Mar 1978, 19 pp. The interaction of man and the visual display unit (VDU) takes place during each of three major tasks, which between them may make up the greater part of the j o b of the worker. Firstly, the worker may be on a telephone unit in a customer service department answering questions and retrieving information filed in the computer's memory. Secondly, he may be entering data directly into a computer memory by utilising the keyboard system or the card entry
114
AppliedErgonomics June 1979
Previous research indicated that peak traffic and the duration of radio-communications were good predictors of behavioural response of air traffic controllers working in air route traffic control centres. In this study the authors investigated if these two measures of workload were generalisable to controllers (ATCs) working in radar facilities serving major airports. 3110 observations were made on radar sectors at the 13 major radar control rooms in the USA. A large number of air traffic variables and communication tasks were measured. Behavioural ratings were made by expert-observer ATCs. The
results replicated previous findings that peak traffic and the duration of radio-communciations functioned as behavioural stressors. Time monitoring and stand-by time were also found to predict behavioural responses. Careful consideration of these and other results led to the conclusion that peak traffic is the most generalisable environmental stressor for ATC's behaviour whereas the other workload measures are more correctly viewed as concomitants of the demand characteristics of ATC work. 10.2.17 (75675)
Stammers, R.B. Human Factors in airfield air traffic control. Ergonomics, Jun 1978, 21.6,483-488. The area of airfield air traffic control is briefly introduced, and potential increases in demands outlined. The tasks involved are described as an initial approach to the problems of developing improved systems. The various methods of information collection and organisation for such tasks are discussed. Possible future developments in systems are mentioned together with their associated ergonomics aspects. 10.2.18 (75677)
Williams, C. Measuring the workloads of social workers. Management Services, Aug 1978, 22.8, 1 0 - 1 7 . This article describes a system for accurately measuring the staffing needs in Social Services fieldwork, based on the needs of the actual cases. The system was developed to overcome the many problems encountered in previous attempts to measure social work and includes provision for the workload measurement of cases closed prematurely or shelved. The author suggests that although the system has been developed specifically in the context of Social Services fieldwork it is likely that the same techniques and methods of analysis can be successfully used in other areas of application where the characteristics of the work are of a similar nature. 10.2.19 (76030)
Borg, G. Subjective aspects of physical and mental load. (Aspects Subjectifs de la Charge Physique et Mentale). (In French.) Le Travail Humain, 1977, 40.2,225-232. Methods of measuring subjective difficulty, effort and other aspects of workload which have been developed by the author and his colleagues are
Auditory processes in man 10.2.8 (76020)
Elliott, L.L. Development of communication aids for the deaf. Human Factors, Jun 1978, 20.3,295-306.
This paper is written primarily for the reader who is not expert in areas of communicative disorders nor actively engaged in research on devices to assit persons with hearing impairments. The intent is to provide a brief introduction and to explain some of the challenges associated with development of sensory aids for the deaf. The discussion also comments on some of the basic human factors questions that deserve attention in the context of improving communication aids.
Information processing and transmission by man 10.2.9 (75635)
Cooper, M.B. The effect of adjacent lamps on the interpretation of a coded flashing lamp. Post Office Research Centre, Martlesham Heath, Ipswich, Post Office Telecommunications Research Department Report No 706, May 1978, I 1 pp. A series of experiments was carried out to investigate the effect of irrelevant adjacent lamps on the speed and accuracy of identifying flashing light codes. In the first experiment, subjects identified the code on a central lamp either in isolation or in a line of three, five or nine lamps. In the second experiment, subjects had to identify the code on a random series of lamps which were specified by means of a numeric display. Subjects in the third experiment searched for a target code on displays of three, five or nine lamps. No effects due to the presence of the adjacent lamps were detected in any of the three experiments. 10.2.10 (75654)
Spitz, G., and Drury, C.G. Inspection of sheet materials - Test of model predictions. Human Factors, Oct 1978, 2 0 . 5 , 5 2 1 - 5 2 8 . The two-stage model of inspection performance suggested in a previous paper was tested in laboratory conditions. Four subjects participated in an experiment to estimate the visual search and decision making components of an inspection task using light circular targets of low contrast on a dark empty field. Predicted and measured performances on the inspection task were compared. It was found that the prediction of independence of component tasks and additivity was upheld. In predicting speed/accuracy trade-off, the model's performance was better
for the high contrast conditions than for the more difficult low contrast conditions.
10.2.11 (76022)
Sinclair, M.A. A collection of modelling approaches for visual inspection in industry. International Journal of Production Research, Jul 1978, 16.4, 2 7 5 - 2 9 2 . The paper outlines the consequences of inspection error for visual statistical quality control schemes and goes on to discuss various approaches that have been adopted to try to estimate the proportion of good items rejected and the proportion of defective items accepted. Brief discussions of these approaches are included, with some criticisms. It is said that most of the approaches used so far have not contributed much towards a model of inspector performance, though there are some recent developments that look a little more encouraging. 10.2.12 (75655) Wade, M.G., and Gold, M.W. Removing some of the limitations of mentally retarded workers by improving job design. Human Factors, Jun 1978, 2 0 . 3 , 3 3 9 - 3 4 8 . The traditionally low level of expectancy of persons with moderate, severe, or profound mental retardation in industrial work settings is reviewed from a human factors viewpoint. A case is made for interfacing the retarded worker into the human machine system b y evaluating performance in terms of information processing ability. Data are reviewed which suggest that there are many industrial tasks at which such a worker can perform well and earn a wage comparable to his non-retarded co-worker. The issue of training workers versus screening workers is discussed as an addtional factor in maximising the role of workers with retardation in industry. The view of the retarded worker as a communication channel and his ability to process information is regarded as a central issue when discussing the optimisation of the person-machine interface. The importance of task analysis in breaking down the task into sub-tasks of acceptable information processing demand is also discussed.
10.2.13 (75657)
Lines, C.J. The effect of motorway signals on traffic speed. Transport and Road Research Laboratory, Crowthorne, Berks. Report No SR-363, 1978, 16 pp.
Applied Ergonomics June 1979
113
The effect on vehicle speed of advisory speed indications shown on motorway signals has been measured at two sites on the M 1 motorway. On an urban section of the motorway at Scratchwood in N London, measurements were made of vehicle speeds before and after a set of signals mounted over the carriageway on a gantry. The signals were set to show an advisory speed of 50 mile/h (80 km/h). Control measurements were also made with the signals switched off. The average speed of light vehicles in the right hand lane was reduced from about 78 to 71 mile/h ( 1 2 5 - 1 1 4 km/h) (9%); in the centre lane from about 69 to 63 mile/h ( 1 1 0 - I 0 1 km/h) (7%%); and in the left-hand lane from about 57 to 55 mile/h ( 9 1 - 8 8 km/h) (4%). Similar measurements were made on a rural section of the motorway at Newport Pagnell where the single signals are mounted on posts in the central reservation. The average speeds of light vehicles in the right-hand lane was reduced from about 77 mile/h to 69% mile/h ( 1 2 3 - 1 1 1 km/h) (91A%); in the centre lane from about 68 to 63 mile/h ( 1 0 9 - 1 0 1 km/h) (7%); and in the left-hand lane from about 55 to 52 mile/h ( 8 8 - 8 3 km/h) (5%). At both sites downstream from the measurement sections, the fast lane was closed for maintenance work. Drivers could not see the temporary signing or the closed lane from the measurement sections, so the speed changes measured would be in response to signal indications.
Factors affecting perceptual-motor performance
system. Thirdly, he may be checking data on the computer against other data he has in non-display form. All of these tasks require concentration on the display screen for long periods of time. The occupational health effects of VDUs derive primarily from the effects of long exposure of the worker to the light, reflection, glare and flickering of the CRT screen. The majority of problems therefore tend to be perceptual and the precipitating causes tend to be multiple and interactive. This report attempts to summarise these and other ergonomic problems of the VDU operator, and provide short, practical recommendations for the installation of VDUs in a clerical environment. A bibliography is provided for further reading. 10.2.15 (75667)
Pepersack, J.P. Human problems arising from the use of microfiches in industry (Problemes Humaine Lies a l'Utilisation des Microfiches dans l'Industrie). (In French.) Cahiers de Medecine du Travail - Cahiers voor arbeidsgeneeskunde, Dec 1977, 14.4, 2 7 9 - 2 8 2 . Abstr in: CIS Abstracts (CIS 78-1480). A typical syndrome is observed in many workers who use microfiche readers: headache, eye fatigue, inflamed conjunctiva, blepharitis, autonomic dystonia, irritability, nervous diathesis, etc. A number of workpost studies revealed several problems: inadequate lighting, difficulty in reading projections, eye strain and nervous strain due to scanning and microfiche, monotonous work, neuropsychic stress. Various solutions are proposed, particularly job rotation. 10.2.16 (75671)
10.2.14 (75665)
Hurst, M.W., and Rose, R.M.
Birnbaum, R.
Objective workload and behavioural response in airport radar control rooms. Ergonomics, Jul 1978, 21.7, 5 5 9 - 5 6 5 .
Health hazards of visual display units with particular reference to office environments. TUC Centenary Institute of Occupational Health, London School of Hygiene and Tropical Medicine, London. Mar 1978, 19 pp. The interaction of man and the visual display unit (VDU) takes place during each of three major tasks, which between them may make up the greater part of the j o b of the worker. Firstly, the worker may be on a telephone unit in a customer service department answering questions and retrieving information filed in the computer's memory. Secondly, he may be entering data directly into a computer memory by utilising the keyboard system or the card entry
114
AppliedErgonomics June 1979
Previous research indicated that peak traffic and the duration of radio-communications were good predictors of behavioural response of air traffic controllers working in air route traffic control centres. In this study the authors investigated if these two measures of workload were generalisable to controllers (ATCs) working in radar facilities serving major airports. 3110 observations were made on radar sectors at the 13 major radar control rooms in the USA. A large number of air traffic variables and communication tasks were measured. Behavioural ratings were made by expert-observer ATCs. The
results replicated previous findings that peak traffic and the duration of radio-communciations functioned as behavioural stressors. Time monitoring and stand-by time were also found to predict behavioural responses. Careful consideration of these and other results led to the conclusion that peak traffic is the most generalisable environmental stressor for ATC's behaviour whereas the other workload measures are more correctly viewed as concomitants of the demand characteristics of ATC work. 10.2.17 (75675)
Stammers, R.B. Human Factors in airfield air traffic control. Ergonomics, Jun 1978, 21.6,483-488. The area of airfield air traffic control is briefly introduced, and potential increases in demands outlined. The tasks involved are described as an initial approach to the problems of developing improved systems. The various methods of information collection and organisation for such tasks are discussed. Possible future developments in systems are mentioned together with their associated ergonomics aspects. 10.2.18 (75677)
Williams, C. Measuring the workloads of social workers. Management Services, Aug 1978, 22.8, 1 0 - 1 7 . This article describes a system for accurately measuring the staffing needs in Social Services fieldwork, based on the needs of the actual cases. The system was developed to overcome the many problems encountered in previous attempts to measure social work and includes provision for the workload measurement of cases closed prematurely or shelved. The author suggests that although the system has been developed specifically in the context of Social Services fieldwork it is likely that the same techniques and methods of analysis can be successfully used in other areas of application where the characteristics of the work are of a similar nature. 10.2.19 (76030)
Borg, G. Subjective aspects of physical and mental load. (Aspects Subjectifs de la Charge Physique et Mentale). (In French.) Le Travail Humain, 1977, 40.2,225-232. Methods of measuring subjective difficulty, effort and other aspects of workload which have been developed by the author and his colleagues are