OCCUPATIONAL APPLICATIONS For both civilian and military pilots, sleep duration and time of day are consistently related to fatigue rating. Fatigue is greater when pilots have fewer hours of sleep or travel later at night or earlier in the morning. Fatigue is also greater as the number of flights flown and the length of flights increase. In addition two-person crews report significantly higher fatigue than three-person crews for long duration flights. Finally, errors increase with less sleep and accident risk becomes higher, especially for duty hours 13 hours or longer. These findings can be used to design fatigue management systems for airline and military aviation operations. TECHNICAL ABSTRACT Background: Fatigue has been on the National Transportation Safety Board's “most wanted list” since 1990 and remains a topic of investigation to this day. Of special interest is the effect of fatigue on aviation safety, especially since fatigue was a contributing factor to several hull loss and fatal aircraft accidents. In 2011, the U.S. Federal Aviation Administration issued the Flight Crew Member Duty and Rest Requirements, which mandated several aspects related to policy, education and awareness training, reporting and monitoring, and performance evaluation. Purpose: Available data on pilot fatigue are summarized to provide input for the development of the mandated fatigue risk management systems. Methods: A literature search was conducted using multiple terms directly and indirectly associated with fatigue. Additionally, outreach was conducted to identify current research that would not yet be in the literature. Results: Studies of aircrew fatigue have been performed on civilian and military aircrews across a wide range of missions and methods, including data collection in flights, simulators, laboratories, surveys of operational pilots, and accident data analysis. For civilian and military pilots, sleep duration and time of day are consistently related to fatigue rating. Fatigue is greater when pilots have fewer the hours of sleep or travel later at night or earlier in the morning. Furthermore, fatigue is greater when the number of flights flown and the length of the flights increase, and errors increase with less sleep. Conclusions: Fatigue is affected by operational factors and can cause degraded performance that can lead to fatal accidents. Some operational factors can be addressed through scheduling of aircrews and flights. This includes addressing aircrew hours of sleep; the number of successive, early wake-ups required for flights; the number of flights flown within a short period; duty length; and the number of pilots per long-haul flight.
OCCUPATIONAL APPLICATIONS Employees play critical roles in improving the performance of operation systems. Work-related health disorders and injuries degrade employees' work performance and hence the performance of the system. Previous studies frequently reported the negative effects of poor ergonomic conditions of the workplace on developing occupational health problems. However, managers lack tools to consider occupational ergonomics aspects, employees' health conditions, and their financial consequences when the performance of systems is optimized. This research provides a hierarchical modeling framework to integrate occupational ergonomics aspects into system performance optimization models. With this modeling approach, ergonomists and human factor practitioners can better influence managers' decisions by developing analytical tools that demonstrate the health, economic, and operational improvement of ergonomics conditions in the system-level analysis.TECHNICAL ABSTRACT Background: Occupational illnesses have negative consequences for employees. They also reduce employees' overall work performance, creating negative economic impacts on companies. Occupational ergonomics studies mostly investigate work-related health and safety aspects of a system to reduce the rate of these health problems for employees. However, they do not usually involve optimizing the performance of a system and do not account for the operational aspects of the system such as demand, workstation interactions, and inventory levels. In contrast, operations management studies usually deal with these operational aspects while optimizing the performance of operation systems. Although human resources are involved in many stages of operation systems, operations management performance optimization models usually use simplifying assumptions regarding human operational characteristics. They rarely include causes and effects of work-related health problems. Purpose and Methods: This article introduces a modeling framework, integrating occupational ergonomics aspects into operations management performance optimization models. It provides a road map for assessing the impact of work-related risk factors, including physical and psychosocial aspects on system performance. Results: An illustrative example demonstrates the applicability of the developed framework in a real situation. The results demonstrate a 0.76% to 3.76% cost growth for a manufacturing system due to the poor ergonomic design of the workplace. Conclusion: By applying this framework, practitioners can find out how the performance of their systems will be enhanced by investing in safer working conditions for employees. Managers can also better assess the economic consequences of a poor ergonomic design and consequent occupational illnesses.
OCCUPATIONAL APPLICATIONS Integrated applications of ergonomics and human factors are crucial for designers of agricultural tools and equipment, to improve performance and to enhance safety and productivity. Tools and equipment that do not fit properly with a user's physical characteristics can cause discomfort and fatigue, and may result in low productivity and a higher incidence of accidents/injuries. For workers in the northeastern region of India, it is often not possible to manufacture or adapt user-compatible tools and equipment due to the limited availability of anthropometric and biomechanical data. The anthropometric database developed here is intended to address this lack of information and to assist in the development of anthropometrically compatible tools and equipment for the Assamese population (residents of "Assam," a state from the northeast region of India). Statistical analyses (principal component and regression analysis) are also reported to help in identifying key anthropometric characteristics to be measured to derive other pertinent anthropometric variables.TECHNICAL ABSTRACT Background: Well-being, efficiency, and productivity of workers can depend substantially on the tools and equipment that they use. To enhance these, along with comfort and safety, tools and equipment should be compatible with the anthropometric characteristics of the intended user. Although anthropometric data are essential for effective equipment design, there is often little published anthropometric data for a given target population, and this is specifically the case for male Assamese agricultural workers. Purpose: To develop an anthropometric database (n = 130) of male agricultural workers within the "Kamrup" district of Assam. Collected data were compared with national and international databases to justify the need to develop local and regional databases. Method: Following a pilot study involving 20 participants, to evaluate the reliability of the anthropometric measurements, the main field study was conducted on 130 male agricultural workers (age range: 17 to 62 years) for a set of 26 body dimensions (along with age and body mass). Results: Mean (standard deviation) of age, stature, and body mass were 37.3 (11.7) years, 1,627.5 (45.9) mm and 55.2 (7.0) kg, respectively. Following principal component analysis of 25 anthropometric variables, six variables were representative of six principal components/factors. Linear regression analysis was used to predict some pertinent body dimensions. Some significant differences were found when comparing the current anthropometric data with databases from other zones of India (Northern, Southern, Eastern, Western, Central, and Northeast) and with male anthropometric data of other countries. Conclusions: Differences in anthropometric data within and between countries indicate that simple adoption of agricultural tools and equipment from specific regions might lead to occupational health hazards in the target population.
OCCUPATIONAL APPLICATIONS Despite many biomechanical risk factors being clearly linked to the development of musculoskeletal disorders, little measurement of the prevalence of physical loads in workplaces is being conducted. Through a collaborative partnership with unions, a health and safety organization, and researchers, this project developed and tested a questionnaire to document exposures to physical workloads in workplaces. Surveys were first completed independently by two members of each organization's joint health and safety committee. The same survey was later completed collectively to arrive at a consensus between the two members. Results of the surveys were then compared to findings from a walk-through conducted by an ergonomist. Substantial to excellent agreement was found between the identification and assessment of exposure levels to 26 types of physical loading by the ergonomist and workplace. Such a survey could be an efficient technique to characterize the loads to which workers are exposed. Such data could have value for targeting prevention activities at a workplace or jurisdictional level.TECHNICAL ABSTRACT Background: The presence and level of exposure to mechanical risk factors can be considered leading indicators in the development of musculoskeletal disorders. Although there are multiple methods for musculoskeletal disorder risk assessment, most of these methods record data related to an individual person performing a specific task. Rather in this questionnaire, we are collecting the exposure data at the workplace level (i.e., for all people experiencing this type of load). Purpose: The aim of this study was to develop and test a survey to document the presence and levels of multiple types of physical loading in a workplace. Methods: A survey requesting information on exposure to 26 types of loading was developed. It was distributed to management and worker representatives for their individual and then their consensus ratings. The same survey was completed by an ergonomist during a site visit. Results: Complete data sets were obtained from 30 workplaces across a variety of sectors. The most prevalent loads reported were sitting, neck bent or twisted, computer use, and carrying loads. For the presence or absence of specific loads, the consensus and ergonomist's ratings agreed well with over 90% for nine of 26 load types and over 70% agreement for 10 other load types. For a calculated exposure index, only four load types differed significantly across the two types of raters. Conclusions: The study demonstrates that a survey completed by individuals familiar with the workplace could be used to document exposure to physical loading at a workplace level in an efficient manner. Such a survey may be useful in understanding the nature and prevalence of such exposures and targeting prevention activities at a workplace or jurisdictional level.
OCCUPATIONAL APPLICATIONS We found differences in muscle activity, joint angles, and discomfort ratings between seated versus standing computerized work, with the standing phase resulting in "better" measures. Given that sit-to-stand workstations are gaining popularity, identifying such differences can help minimize exposure to ergonomic risks during computing tasks-particularly during the standing phase of the work task. For example, workers positioned themselves closer to the work station while standing, which resulted in reduced muscular loads and more neutral joint angles. By adjusting seated postures to more closely reflect standing postures, low level muscle fatigue and discomfort can be minimized.TECHNICAL ABSTRACT Background: Prolonged seated work has been associated with a number of adverse health conditions, and the use of sit-to-stand workstations have been shown to provide benefits for those employed in primarily sedentary work tasks, such as computer tasks. However, little research has been reported on potential differences in musculoskeletal loading and postures during the sit versus stand phases of data entry tasks. Purpose: The purpose of this study was to quantify differences in muscle activity level, joint angle, discomfort in the trunk and upper extremity, and body positioning relative to the workstation while using a sit-to-stand workstation for a simulated data entry task. Methods: A repeated measures design was used to study the effects of computer configuration (desktop, docked laptop with peripherals, and laptop) and sit/stand phase (seated or standing) on muscle activity, posture, and reports of discomfort. Twenty-four participants (12 males and 12 females) completed three cycles of a 20/5 sit-to-stand ratio (20 minutes seated, 5 minutes standing) during a data entry task. Surface electromyography of the shoulders, forearm, and lower back were used to estimate muscle activity levels; electrogoniometers were used to track elbow, neck, and back angles, and discomfort was measured using a body discomfort map. Repeated measures analysis of variance and Tukey's honest significant difference post hoc tests were used to determine statistical differences between conditions. Results: Computer configuration, in general, was not found to significantly affect the dependent measures, though the sit/stand phase did. The seated phase resulted in more non-neutral working postures than standing, which were likely associated with body positioning relative to the workstation and computer. Participants positioned themselves further from the computer and workstation while seated than while standing. Seated work resulted in higher upper trapezius activity than when standing (4.9% versus 2.4%). Conclusions: While sit-to-stand workstations may present long term health benefits, there are likely tradeoffs for the musculoskeletal system-particularly during the seated phase of the work. Workers may benefit from training on body positioning during both phases to ensure neither phase of the work increases musculoskeletal risks.
OCCUPATIONAL APPLICATION: We assessed workload and performance when using two active workstations. Our results, consistent with earlier evidence, indicates that active workstations do not increase physical activity at the expense of reduced performance and operator workload, if these workstations are used for simple tasks that do not require great attention or fine motor control. Active workstations also allowed for more variability in posture and reduced static posture. However, reinforcement of ergonomics recommendations in terms of reducing non-neutral postures may be necessary. TECHNICAL ABSTRACT Background: Over the past 30 years, work has become more sedentary due to increased computer desk work, which has led to the development of major health consequences such as obesity and diabetes. One promising intervention for decreasing sedentariness is the incorporation of active workstations. Objective: We investigated the impact of two active workstations (standing and walking) on workload, task performance, and postural and physiological responses during standard office work tasks. Methods: Using a counterbalanced, within-subjects design, 30 subjects (aged 23.2 [3.1] years) were tested in three workstations: sitting, standing, and walking. A battery of simulated office tasks, including mousing, keyboarding, and cognition tasks, were presented in a randomized order during each trial. Subjective workload was assessed using the NASA-Task Load Index. Performance outcomes included reaction time, number of errors, and total task time. Physiological responses included percent heart rate reserve and heart rate variability. Neck, trunk, and shoulder inclination angles were analyzed to identify differences between workstations with respect to working posture. Results: Compared to sitting, standing and walking both resulted in significantly higher objective measures of workload. While use of walking workstation led to significantly decreased performance on fine motor control tasks, standing did not reduce performance and resulted in improved mousing performance. Both standing and walking allowed for more variability in posture. There was also an indication of more deviation from idle sitting posture while standing and walking compared to sitting. Conclusions: This study contributes to the guidance needed for the use of active workstations, to take advantage of the potential health benefits without sacrificing performance or substantially increasing workload. A standing workstation, properly adjusted based on user anthropometry and ergonomics recommendations, decreased sedentary time, allowed for more postural variability, and enhanced performance on some mousing and cognition tasks, while perceived workload remained consistent with levels while seated.
OCCUPATIONAL APPLICATIONS Subjective health complaints (SHCs)complaints without objective pathological symptoms-such as headaches and heartburn, have become one of the major reasons for short- and long-term sickness absence from work. Unlike musculoskeletal disorders, existing injury/illness surveillance systems do not capture the degree to which nursing personnel experience specific SHCs. Research has mainly focused on musculoskeletal disorders or combined SHCs under "stress outcomes" or "psychosomatic outcomes" without examining these complaints specifically. This study confirms that the occurrence of substantial SHCs is relatively high and that effective strategies are needed to address these conditions in conjunction with musculoskeletal disorders. Although select individual characteristics examined here may only play a minor role in the onset of SHCs, studies including other lifestyle factors (e.g., alcohol consumption, caffeine intake, and activity) may provide further insight to their impact on SHCs. Additionally, results indicate a need for increased focus on the factors originating from the workplace environment.TECHNICAL ABSTRACT Background: Evidence exists regarding the prevalence of and extent to which nurses experience work-related musculoskeletal complaints. However, other types of complaints have not been detailed. Most have fallen under the broad term of "stress outcomes" or "psychosomatic outcomes." Specific complaints need to be examined and understood to fully comprehend work-related subjective health complaints experienced by registered nurses. Objective: This study sought to determine the frequency of subjective health complaint (SHCs, e.g., headaches, heartburn) beyond musculoskeletal disorders among registered nurses and to investigate associations with select individual and organizational factors (e.g., experience, hospital, care area/service, hospital Magnet (R) status [American Nurses Credentialing Center, Silver Spring, MD, USA]). Method: Data were collected on 193 registered nurses from three hospitals using questionnaires to assess SHCs. Descriptive statistics and prevalence rates were reported for substantial cases of SHCs, since low-level complaints can be highly prevalent in the general population. Univariate logistic regression was used to identify significant associations between select individual and organizational factors and substantial SHCs. Results: Rates of substantial SHCs ranged from 1.1%-29.1%. The most frequent complaints were diarrhea or irregular bowel function, allergies, heartburn, headaches, and difficulty falling asleep. Individual, hospital, and care service factors had significant associations with substantial SHCs. Although the majority of SHC rates were higher for registered nurses working in non-Magnet hospitals, Magnet status did not have a significant association with these complaints. Conclusions: SHCs other than musculoskeletal complaints are common among registered nurses. Significant associations with individual and organizational characteristics emphasize the multi-causal etiology of health and well-being and provide additional opportunity for intervention efforts to modify certain lifestyle factors and further in-depth study of organizational factors.
OCCUPATIONAL APPLICATIONS Given advances in augmented reality head-worn display (AR HWD) technologies, "smart glasses" may become an everyday workplace tool in the foreseeable future, allowing workers to perform tasks hands-free while viewing real-time, task-relevant information within their visual field of view. Interviews with experts in several industries (e.g., chemical, medical, manufacturing, distribution) supported such future opportunities for AR HWD development, and underlined important practical concerns that should be overcome to bring smart glasses into mainstream, effective industrial use. Particularly, almost all interviewees believed that poorly designed interfaces for smart glasses may distract workers, yet saw potential in using well-designed AR HWD technology to improve workplace safety and health. This and earlier studies suggest that smart glasses can have important implications for human/task performance as well as workplace safety and health. Future research directions are discussed to promote and accelerate the safe adoption and implementation of AR HWD technologies in the workplace.
The field of human factors and ergonomics (HF/E), since its inception, has been instrumental in developing methods, tools, and solutions when considering cognitive and physical systems independentl...
OCCUPATIONAL APPLICATIONS A higher percentage of young adults with a higher body mass index (BMI) fell after a laboratory-induced trip compared to young adults with a lower BMI, although this difference did not reach statistical significance. Young adults with a higher BMI also exhibited a kinematic response to the trip that was less favorable than adults with a lower BMI. This study provides preliminary evidence that obesity may increase the risk of falls after tripping among young obese workers, and that this increased risk may be due to a less favorable balance recovery response after tripping. Additional larger scale studies are needed to better understand contributing and modifiable factors that can be targeted via intervention or other fall prevention strategies.TECHNICAL ABSTRACT Background: Obese adults are reported to fall at a higher rate than non-obese adults. Purpose: To help determine the reason for this higher fall rate, we quantified fall rates, kinematics at trip onset, and kinematics during the response to a laboratory-induced trip among two groups of young adults with higher and lower body mass indexes (BMI) that approximated obese and healthy-weight ranges. Our focus was on young adults given that they comprise a substantial portion of the workforce. Methods: Twenty-one young adult subjects, including 10 with a lower BMI (19.4–25.7 kg/m2) and 11 with a higher BMI (29.8–42.9 kg/m2), walked along a 10 m walkway at a purposeful speed. During a randomly selected walking trial, an obstacle was raised to elicit a trip. Results: Among the 19 subjects who unambiguously fell or recovered, 30% of subjects with higher BMI fell and 0% of lower BMI subjects fell, but this difference did not reach statistical significance. Among the 15 subjects who used an elevating strategy, all recovered balance, and the only kinematic response variable that differed between BMI groups was that recovery step time was longer among the higher BMI group. Among the four subjects who used a lowering strategy, no statistical analysis was possible due to a small number of subjects, but several measures were consistent with a less favorable kinematic response among the three higher BMI fallers compared to the one lower BMI subject who recovered. Conclusions: This study provides preliminary evidence that obesity may adversely influence fall rate and recovery kinematics after tripping among young adults. Additional larger scale studies are needed to better understand contributing and modifiable factors that can be targeted via intervention.
OCCUPATIONAL APPLICATIONS We tested the boundaries of Parasuraman's vigilance taxonomy to see how porous they are. The degree of porosity is especially informative in mitigating and eliminating the vigilance decrement. These results are relevant to every form of human operation in automated, semi-automated, and autonomous computer-mediated systems.TECHNICAL ABSTRACT Background: When vigilance was stultified, and threatened to become moribund, Parasuraman's vigilance taxonomy revivified the area of research. The taxonomic description features dichotomies across event rate and target comparison type to establish the boundaries of consistent monitoring degradation. This insight implicated resource theory as the causal explanation for the vigilance decrement, founded on the depleting attentional demands of increasing memory load. Despite its manifest value, taxonomic differentiations still require the fixation of constraints that continually have to be challenged and re-evaluated in light of emerging evidence. Such a challenge is erected here. Purpose: To re-examine and re-evaluate the fundamental vigilance taxonomy in order to provide methods to defeat the vigilance decrement, predominantly by design. Methods: Using synthetic integration of accrued knowledge since its original inception down to the present time, our work evaluates and explicates limits to the boundaries represented in the classic vigilance taxonomy. This synthesis serves as a precursor to identifying ways to mitigate or eliminate the vigilance decrement. Results: The thresholds that connote the taxonomic limits are shown to be frangible and the very natures of their identified dis-continuities are themselves informative for methods of remediation. Conclusions: These results are relevant to every form of human operation in automated, semi-automated, and autonomous computer-mediated systems.
OCCUPATIONAL ABSTRACTStand-capable desks have been shown to successfully reduce sedentary behavior in the modern office, but whether their utilization improves cognitive productivity is not known. We compared productivity between stand-capable desk users and traditional seated desk users in a call center environment. Data were collected daily over a continuous 6-month period. We found that increased stand-capable desk use is a likely contributor to increased productivity over traditional seated desk use. These findings indicate that use of stand-capable desks as ergonomic interventions to improve physical health among employees may also positively impact their work productivity.TECHNICAL ABSTRACT Background: Many office employees are spending up to 90% of their workday seated, and employers are considering stand-capable desks as a way to increase physical activity throughout the day. When deciding on adoption of stand-capable workstations, a major concern for employers is that the benefits, over time, may not offset the initial cost of implementation. Methods: This study compared objective measures of productivity over time between a group of stand-capable desk users and a seated control group in a call center. Comparison analysis was completed for continuous 6-month secondary data for 167 employees, across two job categories. Results: Users of stand-capable desks were ∼45% more productive on a daily basis compared to their seated counterparts. Further, productivity of the stand-capable desk users significantly increased over time, from ∼23% in the 1st month to ∼53% over the next 6 months. Finally, this productivity increase was similar for employees across both job categories. Conclusions: These findings suggest important benefits of employing stand-capable desks in the work force to increase productivity. Prospective studies that include employee health status, perceptions of (dis)comfort and preference over time, along with productivity metrics, are needed to test the effectiveness of stand-capable desks on employee health and performance.
OCCUPATIONAL APPLICATIONS This study investigated the effects of a multimodal dual-task paradigm (balance and cognitive tasks) on overall mental workload. The balance task did not affect the performance of the cognitive task, and the presence of the cognitive task led to better balance performance with unstable seating. Simultaneously, measures of overall mental workload showed a general increase when the cognitive task was added and, in some cases, when the balancing task became harder (more unstable). These results generate two important implications. First, the performance levels of two multimodal tasks being done concurrently are insufficient to explain the overall workload in the system. Even if performance is not negatively (or even positively) affected initially, workload increases and may approach or reach overload. Second, any single measure of performance or workload taken in situ might very well be insufficient to explain effectively the way an individual is interacting with their multitasking environment. TECHNICAL ABSTRACT Background: Audition and balance are important aspects of many multitasking environments; auditory signals are used for myriad different alerts and alarms, and balance is pivotal in the realms of factory and construction to avoid falling and risking injury or death. Furthermore, the demands of multiple tasks at once can interact, creating complex environments for which measures of overall workload would be beneficial. Purpose: The goal of this research was to quantify the effects of a cognitive/postural dual-task environment on overall workload. Methods: We utilized a dual-task protocol pairing an auditory discrimination task with a seated balancing task. We then measured performance on both tasks and overall workload using subjective (NASA Task Load Index) and physiological (heart rate variability) measures. Results: Cognitive task performance did not change across different balance conditions, while the presence of the cognitive task decreased postural sway when the participants were unstable. The results regarding workload measures were varied; however, most indicated an increase in workload with the cognitive task. Conclusions: These two results might seem contradictory, with performance in the postural task increasing as the overall workload increases. Taken together, though, they suggest two important conclusions: the need to use more than one method of workload measurement and the importance of understanding the arousal level created by the environment and task difficulty. Designs of auditory alerts in situations involving physical demands should consider arousal levels and possible overload and avoid overvaluing single metrics.
OCCUPATIONAL APPLICATIONS High-intensity work is associated with higher perceived fatigue, which could have a negative effect on both physical and cognitive performance. In particular, it may be unsafe and inefficient for workers to continue high-intensity physical work before complete recovery occurs (i.e., when heart rate returns to baseline levels). However, it is possible for workers to perform mental activities after subjective recovery time. After complete recovery, workers may return to performing the high-intensity physical work. The study evaluated a model of subjective recovery time using gender, relative body mass index, resting heart rate, perceived functional ability, and physical activity rating scores for high-intensity work tasks. With such subjective recovery time estimation, physical and mental work shift schedules that improve work efficiency can be designed. TECHNICAL ABSTRACT Background: Many research studies have investigated the relationship between high-intensity work and cognitive performance. High-intensity work induces higher perceived fatigue, which could have a negative effect on cognitive performance. Few studies have focused on cognitive performance changes during the recovery procedure, however, especially after subjective recovery time. Purpose: Subjective recovery time estimation was examined here, to provide a basis for determining schedules of work that require alternating physical and mental processing. Methods: A total of 47 participants performed reaction tasks aimed at measuring cognitive performance at four time points: before high-intensity work, after high-intensity work, after subjective recovery time, and after complete recovery time. Data from an estimation group (n = 41) were used to derive the subjective recovery time estimate, while the remaining participant data (n = 6) were used for validation. Results: Cognitive performance declined after high-intensity work but improved after subjective recovery time. Subsequent analysis indicated that subjective recovery time was significantly and positively correlated with gender, relative body mass index, and heart rate. Conversely, significant negative correlations were found between subjective recovery time and both perceived functional ability and physical activity rating. Gender, relative body mass index, heart rate, perceived functional ability, and physical activity rating score predicted subjective recovery time (R2 = 0.74). The results of the cross-validation analysis demonstrated that the predicted and actual subjective recovery times were similar. Conclusion: The established model is an efficient tool, using predictor variables that are feasible to obtain in naturalistic work environments, which could be used to estimate subjective recovery time. Along with an existing model that predicts complete recovery time, reasonable arrangements of work schedules that alternate mental and physical work could be designed to improve work efficiency and security.
OCCUPATIONAL APPLICATION Roadway guide signs provide directional and mileage information to specific destinations. These signs are produced by combining different types of retroreflective sheeting materials along with different font types. Some sheeting-font combinations increase nighttime visibility to drivers, while other combinations do not. We compared two types of sheeting materials along with two font types. A field experiment was conducted at night, in the presence of glare from an oncoming vehicle's low beam headlights. A cost comparison was also performed. The most costeffective sheeting-font combination was type XI sheeting and ClearviewHwy (TM) font. These results may be useful for Departments of Transportation to increase legibility distance and the visibility of shoulder-mounted guide signs for drivers, and consequently help increase roadway safety.TECHNICAL ABSTRACT Background: Driver safety remains an important issue, and improving roadway guide sign visibility is an important step in increasing safety on roadways and thus reducing crashes. Currently, two types of retroreflective sheeting materials (type IV and type XI) and either Series E (Modified) or ClearviewHwy font types are used for signs in the United States. Glare from an oncoming vehicle's low beam headlights, however, can create visual difficulty for drivers at night. Purpose: The purpose of this study was to evaluate the performance of two retroreflective sheeting materials and two font types, for use on shoulder-mounted guide signs (i.e., mounted on the shoulder of a roadway) in the presence of glare. Methods: Four sheeting-font combinations, involving type IV and type XI sheeting materials and Series E (Modified) and ClearviewHwy fonts were compared in a field experiment. Participants were asked to read the legend of four signs during nighttime driving, in the presence of glare from an oncoming low beam headlight vehicle. The legibility distance at which the participant read the sign was recorded as the dependent variable. A cost comparison was also performed for the four signs. Results: Type XI sheeting combined with ClearviewHwy font provided the maximum legibility distance. The cost analysis showed that type XI was less expensive over a 60-year timeframe (similar to 9.3% lower) versus type IV. Conclusions: Use of type XI sheeting and ClearviewHwy font is recommended for shoulder-mounted roadway signs to enhance legibility. However, future work is needed to verify these results under more general conditions and with a broader range of participants.
OCCUPATIONAL APPLICATIONS Subjective drowsiness was predicted during a simulated driving task with an accuracy of more than 90%. This was done using a multinomial logistic regression model, using physiological and behavioral measures as predictors. The actual and/or potential applications of these results include the development of a system for predicting drowsiness and presenting drivers a warning. These results can contribute to the enhancement of transportation safety by decreasing the risk of crashes or traffic accidents caused by drowsy driving.TECHNICAL ABSTRACT Background: From the viewpoint of automotive safety, it is useful to detect a decrease in arousal level and to warn drivers of the risk of a traffic accident. Although many measures of drowsy states have been developed, effective methods for predicting drowsy driving states and to warn drivers of these states have not been established. Purpose: The aim of this study was to explore the effectiveness of physiological and behavioral evaluation measures for predicting a drivers' subjective drowsiness using a regression model. Methods: Eight participants completed the study, which involved simulated driving. They were required to steer and maintain their vehicle at the centerline and to maintain the distance between their own car and a preceding car. Physiological measures were obtained (electroencephalography, heart rate variability and blink frequency), along with behavioral measures (neck bending angle, back pressure, foot pressure, and tracking error), and participants reported subjective drowsiness once every minute. Drowsy states were predicted via three multinomial logistic regression models consisting of different independent variables-Model A: both physiological and behavioral measures, Model B: only behavioral measures, and Model C: only physiological measures. For each model, prediction accuracies were examined, and the length of the data window used for predicting drowsiness was explored. Results: When both physiological and behavioral measures were used, prediction accuracy was 96.8%. The interval used for attaining the highest prediction accuracy was 100 seconds (from 120 to 20 seconds before the prediction). When only physiological measures were used, prediction accuracy was 90.2%, and accuracy was 94.9% using only behavioral measures. Conclusions: The proposed multinomial model could attain higher prediction accuracy when both physiological and behavioral measures are used and is potentially useful for the development of drowsiness warning systems.
OCCUPATIONAL APPLICATIONS Our results illustrate the enhanced functional connectivity between motor-related brain regions and high-level cognitive brain regions during the transition period between rest and hand movements. These results suggest that the sensorimotor network is interacting with prefrontal areas during the transition period to maintain the preparation state. Both actual movement and the transition period without actual movement modulate brain activities. Capturing the detailed relationship of movement intention could be utilized to improve precision and latency of anticipation-based brain–computer interfaces. Furthermore, consistent with the neuroergonomic approach, this study demonstrates that functional near-infrared spectroscopy is a suitable tool for region-specific, task-related, and resting-state functional connectivity analysis. Our findings could enhance the development of more intuitive and natural interfaces between human and machine systems in diverse areas. The approach presented here could help create assistive devices that perceive and predict operators' intention of movements. TECHNICAL ABSTRACT Introduction: Traditional and new generations of neuroimaging techniques allow observing the modulation of brain activities during transition periods between rest and physical movement execution. A thorough understanding of the brain activity and functional connectivity changes during these transitions could contribute to increasing the precision and decreasing the latency of anticipation-based brain–computer interfaces, and improving human-system integration in general. Consistent with the neuroergonomic approach, functional near-infrared spectroscopy can monitor the outer cortex during extensive physical movement and in realistic settings using wearable and portable sensors. Methods: In this study, 19 healthy subjects were monitored with functional near-infrared spectroscopy during rest, a fist opening and closing task, and the transition period preceding the task. Functional connectivity analysis was used to evaluate how the transition period preceding the task modulated the brain activities. Results: There were several increases in functional connectivity during the transition period, especially between the right dorsolateral prefrontal cortex and the contralateral primary somatosensory and primary motor cortices, as well as the functional connectivity connecting the contralateral primary somatosensory cortex with the ipsilateral primary somatosensory cortex and the primary motor cortex. Regions located in the sensorimotor networks and right dorsolateral prefrontal cortex were also found to be activated during the transition period. Conclusions: These results demonstrate that the sensorimotor network is interacting with the high-level cognitive brain network during the transition period to maintain the preparation state. Furthermore, functional near-infrared spectroscopy is an emerging tool well-suited for region specific task-related and resting-state functional connectivity analysis. The results and the approach presented here suggest that operators' intention to move can be detected before the actual movement, and that could be employed for development of more intuitive and natural interfaces between human and machine systems.
OCCUPATIONAL APPLICATIONS We evaluated prototype vibrotactile warning systems for supporting pedestrian awareness of approaching hazards. Mobile devices are used by people on the move for leisure and essential task activities in many work domains. While they can be a source of distraction, they also offer sensing capabilities and computing power that can detect and direct attention to approaching hazards. By presenting vibrations from devices distributed around the body, as if embedded in personal protective equipment, these systems can quickly and intuitively convey the risk of collision with a hazard and its approach direction to guide avoidance maneuvers. Results of a simulator study suggest these vibratory warnings improve response time to and avoidance of true hazards, especially when conducting distracting secondary tasks. Future developments of such systems offer promise for increasing safety for distracted pedestrians, as well as for workers in domains that impose high demand on visual and/or auditory senses.TECHNICAL ABSTRACT Background: Mobile devices can be considered essential tools for many daily activities, though there are potential safety risks associated with distraction when hazards are present (e.g., pedestrians near heavily-trafficked roads or workers in industrial settings). Yet, these devices offer onboard sensor and computing capabilities that can be leveraged to improve safety by capturing and guiding attention to approaching hazards. In domains that heavily load vision and audition, vibrotactile cues can reliably support hazard awareness and provide guidance for hazard avoidance. Purpose: We evaluated the effectiveness of prototype vibrotactile warning systems in enhancing recognition of hazards and appropriate avoidance maneuvers. Methods: Participants (n = 27) walked on a treadmill, following a virtual pedestrian path, under varied distracting task conditions. Vehicles, pedestrians, and bicyclists approached from multiple directions, representing "true" (would result in a collision if not avoided) and "false" hazards. Performance was compared with and without each of two experimental displays that presented directional vibrations via devices affixed to suspenders and to an industrial helmet. Signal detection theory and response time analyses were used to determine how well each display supported detection and avoidance of true hazards under each task condition. Results: Each vibrotactile display (suspenders- or helmet-mounted) significantly improved hazard detection in terms of hit rates and response times. Task conditions that included texting and (to a lesser extent) music negatively impacted performance, but decrements were smaller when vibrotactile displays were used. Although conditions involving the vibrotactile displays did not differ significantly in response times or signal detection theory measures, subjective ratings suggested the suspenders display was more comfortable and preferred overall. Conclusions: Vibrotactile displays improved hazard detection and avoidance; however, sensitivity in distinguishing true and false hazards could be improved. Advanced versions of these warning systems offer potential to improve hazard awareness and safety for distracted pedestrians and workers.
OCCUPATIONAL APPLICATIONS The application of ergonomics principles can reduce the number, severity, and costs of work-related musculoskeletal disorders. Increasingly, academic and practitioner research demonstrates that ergonomic improvements also contribute to manufacturing operating efficiency and a company's profitability. This article examines whether it is possible to identify business benefits achieved through ergonomics interventions via an ergonomics award process. The projects, conducted independently at numerous manufacturing locations and submitted to a global company's internal ergonomics award process, were reviewed for effect upon both work-related musculoskeletal disorders and operational efficiency. The results suggest the award process was successful in gathering relevant information about the projects, and that a macroergonomics program methodology along with a participatory approach supported successful results. A cost-benefit estimation showed positive effects in operational efficiency and work-related musculoskeletal disorders reduction. Possible improvements to the award submission process were identified. TECHNICAL ABSTRACT Background: As documented by academics and practitioners, and generally accepted by the popular media, application of ergonomics principles can reduce the number, severity, and costs of work-related musculoskeletal disorders. Research increasingly demonstrates that ergonomic improvements also contribute to manufacturing operating efficiency and a company's profitability. Purpose: To expand the body of practitioner-based knowledge related to the benefits that may be realized through implementing an ergonomics program in industry, focusing on the physical aspects of work. Specifically considered is the importance of a macroergonomic, company-wide process to define how risk assessments are conducted, how interventions are chosen and measured, and how results are summarized. Method: Eighteen case studies, selected from among 166 submitted to a global manufacturing company's internal ergonomics award process were reviewed. Results: A macroergonomics program methodology, in combination with a participatory approach, supported success in terms of reduced work-related musculoskeletal disorder risk and operational efficiency. Specifically, information about how projects were identified and who participated as team members demonstrates the importance of a participatory approach to achieve positive results. Conclusion: The case study results, based upon a practitioner perspective, suggest that operational efficiency and work-related musculoskeletal disorder reduction are often both improved by ergonomic interventions in the workplace, which is consistent with similar findings in earlier research. However, requiring more specific and standardized cost and benefit information in an award submission process is likely to provide more complete information about project results in a manner of value to practitioners, academia, and business. A future challenge is to gain more specific information in a manner that does not significantly add to the workload of individuals leading the projects who, in these case studies, have many responsibilities beyond ergonomics. A collaborative effort between practitioners and researchers to create and test such a method would be of value to both.
OCCUPATIONAL APPLICATIONS Based upon the endurance of their hand and forearm, the maximum duration for holding a computer tablet statically with one hand was less than 10 minutes for many users. In everyday situations, users would likely change posture before this time, but for users whose options are more limited, such as during enterprise use, high levels of fatigue could develop. Therefore, for people in situations where holding a tablet for extended periods of time is required, it would be prudent to change grips frequently, support the tablet on a surface, use aids (such as a stand or strap), hold it with both hands, switch to alternative tasks, and/or take breaks.TECHNICAL ABSTRACT Background: The use of tablet computers at home and in the workplace has rapidly increased in recent years. Tablet users may hold them for extended periods, increasing the risk of developing fatigue and potential musculoskeletal disorders. Purpose: The goals of this study were to estimate the biomechanical loading on the forearm and hand when holding a tablet computer and to assess the effects of orientation, mass, and the execution of touch gestures on this loading. Methods: Multiple parallel approaches were used to assess an unsupported single-handed grip: maximum load, maximum holding time, biomechanical models to estimate strength demands, ratings of perceived exertion, and grip pressure. Ten males and 10 females participated. Results: A majority (75%) of the participants adopted a modified lateral pinch grip. Using the maximum load method, females exerted a significantly higher percentage of their maximum voluntary contraction than males in landscape orientation (18.5% versus 13.5% maximum voluntary contraction) but not in portrait orientation. In portrait orientation, maximum holding time was 11.5 minutes for females and 15.9 minutes for males. Orientation, but not gesturing, had statistically significant main effects on loading. Conclusions: Holding a tablet one-handed for an extended period of time, as might be found in some enterprise settings, was found to be very fatiguing for the hand; it would thus be prudent for such users to use both hands, support aids, frequent posture changes, or breaks involving rest or alternative tasks.
