• Journal of the Ergonomics Society of Korea
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• v.29 no.4
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• pp.687-691
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• 2010

Workload assessment is one of the important elements of the human factors evaluation for the nuclear power plants in operation. This paper describes a further study upon the additional elements of the workload which elements should be considered in the subjective workload assessment. We have tried to predict the burden of the work and to improve the work through a comparison of the objective workload and the subjective workload in the previous studies in nuclear power plants. However, there is a restriction to perform a precise assessment because of the limitations of the method itself. The objective workload assessment is performed by relative comparison using the quadrant analysis with objective workload and subjective workload because there were no clear criteria of objective workload assessment. And the subjective workload assessment is performed by NASA-TLX (NASA Task Load Index) which includes six evaluation dimensions of subjective workload. NASA-TLX is difficult to grasp the other aspects that could influence on the subjective workload because the analysis relies on predetermined assessment items. We conduct a factor analysis between the factors that affect the workload and the assessment adopted from ISO 10075 and NASA-TLX. At the same time, this study suggests other evaluation elements which can be added for subjective workload assessment except for evaluation elements of NASA-TLX.

• Journal of the Ergonomics Society of Korea
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• v.32 no.2
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• pp.167-177
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• 2013

Objective: This study aims to compare the usefulness of subjective measures which are comprised of existing methods like NASA-TLX, Bedford-scale and ZEIS and newly developed method like DALI in measuring drivers' mental workload in terms of validity, sensitivity and diagnosticity. Background: Nowadays, with the development of intelligent vehicle and HMI, mental workload of driver has become more and more important. For this reason, the studies on drivers' mental workload about driving situation and the use of information technology equipment such as mobile phones and navigations were conducted intensively. However, the studies on measuring drivers' mental workload were rarely conducted. Moreover, most of studies on comparison of subjective measures were used with performance based measure. However, performance based measures can cause distraction effect with subjective measures. Method: Participants (N=19) were engaged in a driving simulation experiment in 2 driving contexts (downtown driving and highway driving context). The experiment has 2 sessions according to driving contexts. The level of difficulties by driving contexts were adjusted according to existence of intersections, traffic signs and signals, billboards and the number of doublings. Moreover, as criteria of concurrent validity and sensitivity, the EEG data were recorded before and during the sessions. Results: The results indicated that all subjective methods were correlates with EEG in high-way driving. On the contrary to this, in downtown driving, all subjective methods were not correlates with EEG. In terms of sensitivity, multi-dimensional scales (NASA-TLX, DALI) were the only ones to identify differences between high way and downtown driving. Finally, in terms of diagnosticity, DALI was the most suitable method for evaluating drivers' mental workload in driving context. Conclusion: The DALI as newly developed method dedicated to evaluate driver's mental workload was superior in terms of sensitivity and diagnosticity. However, researchers should consider the characteristics of each subjective method synthetically according to research objective by selecting the method in subjective measures. Application: The results of this study could be applied to the intelligent vehicle and next generation of HMI design to decrease mental workload of driver and for the development of new subjective method in vehicle domain.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.45
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• pp.145-154
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• 1998

The effects of secondary task on driving performance and subjective workload were investigated during a simulated driving. The driving performance was determined by the appropriateness of break timing. The driving simulator was provided by the Korea Road Traffic Safety Association. The subjective workload was tested by using a multidimensional measure such as NASA-TLX. Road was categorized into two types: narrow alley and wide street. The secondary task included pushing the number on the cellular phone, pushing radio channel, and conversing with a passenger. Seventeen subjects volunteered in the study. The data were analyzed by using SAS. Results showed that using the cellular phone and pushing channel during driving caused 3∼22% decline of driving performance and 42∼59% increase of subjective workload respectively. These results indicated that the secondary task could be potentially dangerous although there was not a significant performance decrease due to the notable increase of mental workload. In the future, if we can use a more sensitive and realistic driving simulator, the effects of secondary task under a dynamic driving situation can be investigated.

• Proceedings of the ESK Conference
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• 1997.10a
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• pp.433-436
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• 1997

Automobile assembly tasks consist of many kinds of manual work which are very stressful to workers because of repetitive poor working postures and dealing heavy weights. To decrease the level of workload, it is necessary to evaluate the workload quantitatively. In this study, a workload evaluation method based on EMG was experimentally evaluated. We measured EMG at 6 main muscles with 2 healthy male workers during doing 9 assembly tasks, which were selected as high workload jobs. The tasks were decomposed into 36 elementary tasks. The workload was calculated through an equation with %MVIS and work duration time. To evaluate the result, subjective discomfort on the tasks was assessed by 29 workers. By the calculated workload, we were able to ranked the workload of tasks, elementary tasks. The comparison between the EMG-based workload and subjective rating showed a positive correlation(P-value=0.0246). We think it is possible to adapt the EMG-based workload evaluation technique to all assembly tasks by expending the experi- ment size.

• Journal of the Ergonomics Society of Korea
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• v.18 no.2
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• pp.103-120
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• 1999

The purpose of this study was to evaluate the manual workload in repetitive wrist and finger motion. To evaluate manual workload, angular displacement of the joint, EMG of the muscle and subjective rating were studied. Both wrist motion and finger motion were studied. A screw-driving task was used for the wrist motion experiment. A keyboard typing task was used for the finger motion experiment. All finger joint angles and wrist angles were measured by an angle-measuring glove($CyberGlove^{TM}$, Virtual Technologies, Inc.). Surface EMG was recorded from FCU muscle and FDS muscle simultaneously with the angle measurement. Subjective ratings of exertion were also recorded using the modified Borg's CR-10 scale. Repetition rates of 0.5, 1, 2 motions per second were used with each task. As a result, manual workload increased with increasing repetitiveness. Peak spectral magnitude and frequency components corresponded closely with joint angular displacement amplitudes and repetition rates. Results of the correlation analysis showed that there were significant correlation among EMG, frequency-weighted motion and subjective measurement. Both EMG and frequency-weighted filtering showed consistent workload estimation with increasing task frequency. Subjective ratings showed slight over-estimation of the workload as the task frequency is increased.

• Journal of Korean Society of Transportation
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• v.19 no.3
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• pp.45-58
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• 2001

Subjective mental workload assessment technique becomes a standard human factors and human-machine interface evaluation tool for the evaluation of ITS(Intelligent Transport Systems)-oriented information systems as well as the drivers visual activity analysis, physiological indices(GSR, EEG, ECG, etc.), secondary task performance, reaction time. vehicle control parameters(speed, steering behavior, accelerator control) that are widely applied for transportation and vehicle systems to evaluate the safety, to decide the system or design alternatives, and to establish the design guidelines. This paper reviewed and compared the most globally employed four mental workload assessment techniques that have been designed for the use of various human-machine systems and ITS-oriented in-vehicle information systems. NASA-TLX(National Aeronautics and Space Administration-Task Load Index). SWAT(Subjective Workload Assessment Technique), MCH(Modified Cooper-Harper) scale, and recently developed RNASA-TLX(Revision of NASA-TH) were compared in terms of sensitivity and subjective evaluations to derive the human-machine interface evaluation guidelines for the application of ITS-oriented in-vehicle information systems. Then, experiment results supported that RNASA-TLX is the prospective tool for the mental workload assessment of ITS-oriented in-vehicle information systems.

• IE interfaces
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• v.16 no.2
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• pp.222-228
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• 2003

Computer-dominated jobs and industrial automation have rapidly created work-related musculoskeletal disorders(WMSDs) and WMSDs are also founded in employees of other general industries. WMSDs has been growing problems for Korean industries with higher incidence rate every year. The objective of this paper is to analyze the effects of the neck muscle workload according to postures(joint angle) and load weights. Seven male students participated in this study. Neck workload was rated on each person using a Borg's CR-10 scale. ANOVA showed that the CR-10 ratings were statistically significant according to postures and load weights. To reduce the large number and severity of WMSDs, which employees have been experiencing, we need to redesign the job in workplace so that we can control hazards that are reasonably likely to be causing or contributing to the WMSDs. The results of this study can be used to establish the safety criteria of joint angle and weight of neck workload.

• Journal of the Ergonomics Society of Korea
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• v.30 no.2
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• pp.349-356
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• 2011

Objective: The purpose of this study was to analyze the risk factors of the musculoskeletal workload of mid-old-age female caregivers by identifying work postures and subjective symptoms. Method: This study was carried out on a total of 206 subjects 206 mid-old-age caregivers(45~65 years old) from November 2009 to April 2010: 206 mid-old-age caregivers (45~65 years old) at the long-term hospital. A questionnaires survey on general factors and subjective symptoms of subjects was conducted. The risk factors of the musculoskeletal workload evaluation method is based on OWAS, RULA, REBA according to occupation properties. Results: The analysis of the rates of the subjective symptoms showed that 78.6% subjects experience low back pain. The analysis of the work type showed that transfer is the highest rate(36.3%) and position change is the second(18.2%). The analysis of the work postures showed that the thrusted back with twisting position over $20^{\circ}$ is highest rate(37.4%), the bended back forward with twisting position is the second(27.5%). Conclusion: This study suggested that the need of preventive education for caregivers and workload improve. It is hoped that subsequent study on the difference of subjective symptoms between educated caregivers and non educated caregivers will be conducted.

• Journal of the Korean Society of Marine Environment & Safety
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• v.2 no.1
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• pp.35-45
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• 1996

The assesment of the safety of ship's transit in a curved narrow channel consists of the maneuvering safety determined by the chance of running aground, the maneuvering difficulty determined by ship's workload, and shiphandler's subjective evaluation. In this study to examine the correlation between shiphandler's subjective evaluation and the maneuvering risk, the real-time and full-mission shiphandling simulator in the Korea Marine Training & Research Institutes(KMTRI) was utilized. On the conning bridge of the shiphandling simulator, 50 experienced masters conducted the modeled vessel of 60,000 deadweight tonnage along the designed channel under 3 different environmental conditions. The findings were as follows : (1) The frequencies of stress levels, work difficulties, vessel controllability and overall workload of shiphandlers are similar irrespective of environmental conditions and they are able to be represented as shiphandler's subjective evaluation. (2) It s possible to assess and analyze theoretically the correlation between the shiphandler's subjective evaluation and maneuvering risk under each environmental condition by quantifying the data obtained from the test. The results are as follows : ① As the degree of maneuvering risk increases, the shiphandler's subjective evaluation increases sharply near the curvature area of the designed channel. ② In the area of the curvature of the designed channel, maneuvering risk sincreases sharply with the danger of running aground under the environmental condition of current and wind coming from the stern.

• IE interfaces
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• v.10 no.1
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• pp.145-154
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• 1997

In developing the HMI(Human-Machine Interface) evaluation system for the IVNS(In-Vehicle Navigation System), design guidelines and evaluation methods are the most crucial problems for its use and efficiency. As the part of this system, focused on the final product of the database, subjective mental workload assessment is seriously considered to evaluate the driver's own driving task using the IVNS. This paper suggests the methodology for the ergonomic assessment of the IVNS that corresponds to the subjective measurement of the driver's mental workload by rating his or her own driving task. For this approach, Revision of NASA-Task Load Index(RNASA-TLX) was developed which translated and revised the version of NASA-TLX that is generally accepted an efficient and powerful method for evaluating the in-vehicle information systems. To verify the RNASA-TLX, an experiment was conducted in a real road situation, because the result of the laboratory approach is uncertain and has the differences from the real road test.