NASA-TLX Workload Research Articles

The Association Between Workload and Needlestick Injuries Among the Nurses in the Hospitals Affiliated with Ahvaz University of Medical Sciences

Background: This study investigated the workload and its effects on the prevalence of needlestick injuries (NSIs) among the nurses in the hospitals affiliated with Ahvaz University of Medical Sciences (AUMS). Methods: In this cross-sectional study, 416 registered nurses working in different wards of the hospitals affiliated with Ahvaz University of Medical Sciences (AUMS) were randomly selected. Data collection instruments were a demographic questionnaire and NASA-TLX workload questionnaire. Results: The prevalence of NSIs in the total work experience and the last year were 72% and 50%, respectively. The mean total score of NASA-TLX calculated to the extent of 78.27 ± 12.2. The regression modeling demonstrated that NSIs significantly correlated with patients treated/d (OR: 1.136, CI: 1.02 - 1.27, P value: 0.002), Timing of injury (OR: 2.13, CI: 1.20 - 3.79, P value: 0.010), and the third dimensions of NASA-TLX index (time pressure) (OR: 1.031, CI: 1.02- 1.05, P value: < 0.001). Conclusions: The study showed a high prevalence of NSIs among nurses. Corrective measures such as planning training programs targeting at using personal protective equipment (PPE), modification of work schedule by limiting working hours and the number of shifts per month, and providing sufficient human resources are essential for the effective prevention of NSI incidents among the studied nurses.

Dyadic Team Interaction and Shared Cognition to Inform Human-Robot Teaming

Project overview. The current research aims to understand how human operators effectively team with urban search robot teammates in a dynamic and complex task environment. With that in mind, we examined how shared cognition and restricted language capabilities impact performance of human dyadic teams using a simulated Minecraft task environment. In this human dyadic team, an internal teammate (comparable to robot) identifies the location of victims while navigating inside a game environment that reflects a collapsed building; and an external teammate (comparable to operator) sees their teammate's actions from a different screen and guides them through the environment, tracking the location of victims on a map as they go. In order to examine the effects of language and shared cognition, a two by two design was chosen: (1) in the communication manipulation, participants are either able to communicate using natural language or the internal participant’s communication is limited to three-word utterances; and (2) in the shared cognition manipulation, either the internal participant is made fully aware of the external participant’s restricted representation of the environment and inaccurate map or the internal is unaware of these challenges. Method. This study used a simulated search task, in the Minecraft gaming environment, where two humans acted as a human-robot search team (Bartlett &amp; Cooke, 2015). After signing consent forms, two randomly selected participants completed a half-hour training session for their individual role. Both participants sat in the same room but had a divider between them, and then, interacted to complete a 15-minute simulated search task. The Minecraft environment resembled an office structure with interspersed green, blue, and pink blocks that represented potential targets. Blue and green blocks were meant to represent survivors, whereas pink blocks represented hazards. Pressing a button on green blocks counted positively towards the team’s performance, whereas pressing a button on pink blocks counted negatively towards the team’s performance. Blue blocks were time-sensitive, such that pressing a button on them before eight minutes into the scenario counted positively toward performance, but pressing the button after that time counted against performance. Pressing the button on any block more than once counted negatively towards the team’s performance. A map of this environment was also made available. Inconsistencies were intentionally introduced, such as missing walls, additional walls, and misplaced doorways to simulate a damaged building, none of which were depicted on the map. Due to the dynamic nature of the task, effective communication and coordination between the dyads is required for effective performance. Several measures were obtained in this research: team performance, situation awareness, NASA TLX workload, team verbal behaviors, team communication flow, and demographics. In the interest of space, we only present team performance, a determinism measure (served as an index of flexible behavior and was estimated from team communication flow, using Recurrence Quantification Analysis (Marwan, Carmen Romano, Thiel, &amp; Kurths, 2007), and NASA TLX workload. Results and conclusion. The primary findings from this study are that: 1) teams in the natural language and shared model conditions, performed better than teams with the limited language and restricted model, respectively; 2) when the internal participant is unaware of the challenges of the external, the external perceives higher workload than when there is a shared cognition; 3) teams with natural language and shared model demonstrated more predictable behavior than the other teams; 4) some amount of systems predictability is good but too much predictability is not good in the system – this also confirms another study: Demir, Likens, Cooke, Amazeen, &amp; McNeese, InReview. Overall these results indicate that effective team interaction and shared cognition play an important role in human-robot teaming performance. Acknowledgements. Human-Robot Dyad research was partially supported by ONR Grant N0014-13-1-0519 to PI: Subbarao Kambhampati (Program Managers: Marc Steinberg). We also acknowledge assistance of data collection Aaron Bradbury, Emily Gran, Jocelyn Martinez, and Madeline Niichel.

Eco-driving for the first time: The implications of advanced assisting technologies in supporting pro-environmental changes

Eco-driving assistance devices are being introduced to reduce CO2 emissions, but the overall changes in the user behavior have not been sufficiently explored. While in-vehicle driver advanced systems are designed to support a single driving task (e.g. reducing emissions), they also imply the adoption of a different driving behavior and different driving attitudes in order to be efficient. Adopting for the first time a new driving style could affect driver's acceptance and undermine new technologies' efficacy. Purpose of the present research is to measure and evaluate the user's responses to first-time use of eco-driving assisting technology. Driver's performances in a virtual simulator were compared between experimental and a control group. The actual driving parameters and CO2 emissions were recorded and compared to the optimal eco-driving style calculated by CarMaker software. The cognitive costs of the new driving style were measured by changes in the modulation of autonomic nervous system and NASA-TLX workload scale. Acceptance of the assisted driving style and general eco-friendly attitudes were analyzed by self-reported measures. Results show that being exposed for the first time to eco-driving technology produces a reduction of cumulate fuel consumption only due to speed reduction, and not to changes in the driving style parameters, as recommended by the assisting software. Overall CO2 emissions of eco-driving group were not different from the control group. Rather, the first time use of the eco-driving assistance increases perceived fatigue and the physiological cardiac autonomic balance related to increased workload over time. These difficulties show that eco-driving style cannot be simply adopted by following the assistance device indications. It seems rather a process, which requires specific support during in the first driving-interaction with eco-driving technology. The design of assistance device that aims to change the driving style, could benefit from the measurement of the user's workload to avoid primacy effect that potentially undermine technology efficacy in supporting user-sustainable behaviors.

An Investigation of the Usability Issues of Home-based Video Telemedicine Systems with Geriatric Patients

Telemedicine is the use of technology to provide and support healthcare when distance separates the clinical service and the patient. This system is rapidly replacing the conventional method of in-person clinical visits. More than seventy percent of the geriatric population is predicted to need long-term healthcare; telemedicine could potentially support their increased healthcare needs. However, for increased user acceptance, it is important to investigate the usability of telemedicine systems. This study aims to investigate the usability issues associated with geriatric patients using home-based video telemedicine systems. Four home-based video telemedicine systems were chosen for this study: (1) Doxy.me, (2) Polycom, (3) Vidyo and (4) VSee. Using a between-subjects experimental design, 20 participants were randomly assigned to one of these four conditions. They were asked to complete a demographic questionnaire, followed by the completion of representative tasks on the telemedicine platform. This is followed by a retrospective think-aloud session at the end of which, the participants completed a NASA-TLX workload survey, an IBM Computer System Usability Questionnaire (IBM-CSUQ), and a post-test subjective questionnaire. Issues faced by the participants include downloading application plug-ins, locating icons and the size of the icons.

Agent Reasoning Transparency’s Effect on Operator Workload

We examined how varying the transparency of agent reasoning affected operator workload in a route selection task, and how the differing measures of workload compared in assessing and understanding cognitive workload. Participants guided a three-vehicle convoy safely through a simulated environment of which they had a limited amount of information, while maintaining communication with command and monitoring their surroundings for threats. The intelligent route-planning agent assessed potential threats and suggested changes to the convoy route as needed. Each participant was assigned to one of three agent reasoning transparency conditions. Contrary to our hypothesis, NASA-TLX Global workload measures indicated that workload decreased slightly as access to agent reasoning increased. However, psychophysical measures of workload disagreed with NASA-TLX global results. Comparison of individual NASA-TLX workload factors with the psychophysical measures indicated that performance satisfaction was highest in the intermediary transparency condition, and the addition of ambiguous information in the highest transparency condition increased effort and resulted in increased complacent behavior. Recommendations for future workload analysis are offered.

Device- and system-independent personal touchless user interface for operating rooms : One personal UI to control all displays in an operating room.

In the modern day operating room, the surgeon performs surgeries with the support of different medical systems that showcase patient information, physiological data, and medical images. It is generally accepted that numerous interactions must be performed by the surgical team to control the corresponding medical system to retrieve the desired information. Joysticks and physical keys are still present in the operating room due to the disadvantages of mouses, and surgeons often communicate instructions to the surgical team when requiring information from a specific medical system. In this paper, a novel user interface is developed that allows the surgeon to personally perform touchless interaction with the various medical systems, switch effortlessly among them, all of this without modifying the systems' software and hardware. To achieve this, a wearable RGB-D sensor is mounted on the surgeon's head for inside-out tracking of his/her finger with any of the medical systems' displays. Android devices with a special application are connected to the computers on which the medical systems are running, simulating a normal USB mouse and keyboard. When the surgeon performs interaction using pointing gestures, the desired cursor position in the targeted medical system display, and gestures, are transformed into general events and then sent to the corresponding Android device. Finally, the application running on the Android devices generates the corresponding mouse or keyboard events according to the targeted medical system. To simulate an operating room setting, our unique user interface was tested by seven medical participants who performed several interactions with the visualization of CT, MRI, and fluoroscopy images at varying distances from them. Results from the system usability scale and NASA-TLX workload index indicated a strong acceptance of our proposed user interface.

Establishing an instrumented training environment for simulation-based training of health care providers: An initial proof of concept

Objective: Several decades of armed conflict at a time of incredible advances in medicine have led to an acknowledgment of the importance of cognitive workload and environmental stress in both war and the health care sector. Recent advances in portable neurophysiological monitoring technologies allow for the continuous real-time measurement and acquisition of key neurophysiological signals that can be leveraged to provide high-resolution temporal data indicative of rapid changes in functional state, (i.e., cognitive workload, stress, and fatigue). Here, we present recent coordinated proof of concept pilot project between private industry, the health sciences, and the USA government where a paper-based self-reporting of workload National Aeronautics and Space Administration Task Load Index Scale (NASA TLX) was successfully converted to a real-time objective measure through an automated cognitive load assessment for medical staff training and evaluation (ACLAMATE). Methods: These real-time objective measures were derived exclusively through the processing and modeling of neurophysiological data. This endeavor involved health care education and training with real-time feedback during high fidelity simulations through the use of this artificial modeling and measurement approach supported by Aptima Corporation's FuSE2, SPOTLITE, and PM Engine technologies. Results: Self-reported NASA TLX workload indicators were converted to measurable outputs through the development of a machine learning-based modeling approach. Workload measurements generated by this modeling approach were represented as a NASA TLX anchored scale of 0–100 and were displayed on a computer screen numerically and visually as individual outputs and as a consolidated team output. Conclusions: Cognitive workloads for individuals and teams can be modeled through use of feed forward back-propagating neural networks thereby allowing healthcare systems to measure performance, stress, and cognitive workload in order to enhance patient safety, staff education, and overall quality of patient care. The following core competencies are addressed in this article: Medical Knowledge, Interpersonal Skills, Patient Care, and Professionalism.

The Relationship between Mental Workload and Prevalence of Musculoskeletal Disorders among Welders of Tehran Heavy Metal Structures Company in 2016

workload refers to the amount of effort put in by the mind during the accomplishment of a duty. It essentially has to do with individuals’ mental capacity and the way they receive and process information in order to make decisions and take appropriate actions. The present study aimed at investigating the relationship between mental workload and prevalence of musculoskeletal disorders among welders of Tehran Heavy Metal Structures Company. This cross-sectional descriptive study was conducted in 2016. The sample included 100 welders working at Tehran Heavy Metal Structures Company. Sampling was done by census method. A demographic features questionnaire, NASA-TLX workload questionnaire, and Nordic Questionnaire were used for data collection. Data were analyzed by the use of SPSS (Version 22). Various data analysis procedures, including independent samples t-test, Pearson correlation, chi-square, and Fisher’s exact test, were employed. The mean of participants’ overall score in mental workload was 65.88 ± 21.15. Eighty four percent of the studied welders reported that they had experienced musculoskeletal disorders during the past 12 months (leading to the study), with the highest prevalence being recorded for waist (65%). Furthermore, the results of Pearson correlation indicated that there was a significant relationship between the prevalence of disorders in the legs and physical demand (P = 0.032). Also, a considerable association was observed between disorders in the wrist / hand and overall NASA mental workload score during the past 12 months (P = 0.021). Mental workload and the prevalence of musculoskeletal disorders are relatively high among welders. Waist was the most important risk factor among the participants studied. Future studies should attempt to detect risk factors that cause such disorders and suggest ways to reduce or prevent these problems among welders as much as possible.

Impact of novel shift handle laparoscopic tool on wrist ergonomics and task performance.

Laparoscopic tool handles causing wrist flexion and extension more than 15° from neutral are considered "at risk" for musculoskeletal strain. Therefore, this study measured the impact of laparoscopic tool handle angles on wrist postures and task performance. Eight surgeons performed standard and modified Fundamentals of Laparoscopic Surgery (FLS) tasks with laparoscopic tools. Tool A had three adjustable handle angle configurations, i.e., in-line 0° (A0), 30° (A30), and pistol-grip 70° (A70). Tool B was a fixed pistol-grip grasper. Participants performed FLS peg transfer, inverted peg transfer, and inverted circle cut with each tool and handle angle. Inverted tasks were adapted from standard FLS tasks to simulate advanced tasks observed during abdominal wall surgeries, e.g., ventral hernia. Motion tracking, video analysis, and modified NASA-TLX workload questionnaires were used to measure postures, performance (e.g., completion time and errors), and workload. Task performance did not differ between tools. For FLS peg transfer, self-reported physical workload was lower for B than for A70, and mean wrist postures showed significantly higher flexion for in-line than for pistol-grip tools (B and A70). For inverted peg transfer, workload was higher for all configurations. However, less time was spent in at-risk wrist postures for in-line (47%) than for pistol-grip (93-94%), and most participants preferred Tool A. For inverted circle cut, workload did not vary across configurations, mean wrist posture was 10° closer to neutral for A0 than B, and median time in at-risk wrist postures was significantly less for A0 (43%) than for B (87%). The best ergonomic wrist positions for FLS (floor) tasks are provided by pistol-grip tools and for tasks on the abdominal wall (ventral surface) by in-line handles. Adjustable handle angle laparoscopic tools can reduce ergonomic risks of musculoskeletal strain and allow versatility for tasks alternating between the floor and ceiling positions in a surgical trainer without impacting performance.

An Investigation of the Effectiveness of Navigational Aids in a Virtual Environment

Past research emphasizes the potential of using Virtual Reality (VR) in education because of its ability to provide the user with a sense of immersion that promotes learning and growth. However, navigation in this environment has been found to be challenging. To address this issue, this pilot study developed a virtual reality based application to reinforce the knowledge of safety protocols in a manufacturing setting. This environment included a simulated assembly line, and participants were asked to identify and tag hazards including virtual workers committing safety violations. This research then investigated the effectiveness of four navigational aids using a between-subjects experimental design. Twenty participants underwent video-based training focused on potential safety violations in a manufacturing environment. They were subsequently exposed to the virtual environment and provided with training in identifying and classifying violations. The participants were then asked to identify safety hazards that were placed throughout the virtual manufacturing facility. The dependent variables included the time spent in the virtual environment, the number of violations identified, eye gaze measures, the NASA-TLX workload, and computer systems usability measures. Statistically significant differences were found for the dependent measures of number of violations identified, workload and usability. The results suggest that both maps and arrows embedded on the floor have the potential to enhance usability with reduced workload.

Development of the Team Workload Questionnaire (TWLQ)

In the present paper we developed the Team Workload Questionnaire (TWLQ). Despite extensive workload studies, little research has been conducted on the workload experienced by teams. Team workload has largely been ignored by research with no validated theory constructed or dedicated team workload measures available to researchers and practitioners. The TWLQ items were generated based on the NASA-TLX and team workload theory. We examined 216 members of sports team completing a team workload measure after games or practice. Principal Axis Factoring method with Direct Oblimin rotation indicated three separate factors for the TWLQ with the factors classified as Task Workload, Team Workload, and Task-Team Balancing. The TWLQ may be a useful subjective measure that can be used to assess the workload demand in team tasks. It provides researchers a tool to advance the understating of team workload and gives practitioners the means to assess the workload demands of team tasks.

Upper limb muscular activity and perceived workload during laryngoscopy: comparison of Glidescope® and Macintosh laryngoscopy in manikin: an observational study

BackgroundThe interaction between operators and their working environment during laryngoscopy is poorly understood. Numerous studies have focused on the forces applied to the patient's airway during laryngoscopy, but only a few authors have addressed operator muscle activity and workload. We tested whether different devices (Glidescope® and Macintosh) use different muscles and how these differences affect the perceived workload. MethodsTen staff anaesthetists performed three intubations with each device on a manikin. Surface electromyography was recorded for eight single muscles of the left upper limb. The NASA Task Load Index (TLX) was administered after each experimental session to evaluate perceived workload. ResultsA consistent reduction in muscular activation occurred with Glidescope® compared with Macintosh for all muscles tested (mean effect size d=3.28), and significant differences for the upper trapezius (P=0.002), anterior deltoid (P=0.001), posterior deltoid (P=0.000), and brachioradialis (P=0.001) were observed. The overall NASA-TLX workload score was significantly lower for Glidescope® than for Macintosh (P=0.006), and the factors of physical demand (P=0.008) and effort (P=0.006) decreased significantly. ConclusionsGreater muscular activity and workload were observed with the Macintosh laryngoscope. Augmented vision and related postural adjustments related to using the Glidescope® may reduce activation of the operator's muscles and task workload.

Proficiency-based training for robotic surgery: construct validity, workload, and expert levels for nine inanimate exercises

We previously developed nine inanimate training exercises as part of a comprehensive, proficiency-based robotic training curriculum that addressed 23 unique skills identified via task deconstruction of robotic operations. The purpose of this study was to evaluate construct validity, workload, and expert levels for the nine exercises. Expert robotic surgeons (n = 8, fellows and faculty) and novice trainees (n = 4, medical students) each performed three to five consecutive repetitions of nine previously reported exercises (five FLS models with or without modifications and four custom-made models). Each task was scored for time and accuracy using modified FLS metrics; task scores were normalized to a previously established (preliminary) proficiency level and a composite score equaled the sum of the nine normalized task scores. Questionnaires were administered regarding prior experience. After each exercise, participants completed a validated NASA-TLX Workload Scale to rate the mental, physical, temporal, performance, effort, and frustration levels of each task. Experts had performed 119 (range = 15-600) robotic operations; novices had observed ≤ 1 robotic operation. For all nine tasks and the composite score, experts achieved significantly better performance than novices (932 ± 67 vs. 618 ± 111, respectively; P < 0.001). No significant differences in workload between experts and novices were detected (32.9 ± 3.5 vs. 32.0 ± 9.1, respectively; n.s.). Importantly, frustration ratings were relatively low for both groups (4.0 ± 0.7 vs. 3.8 ± 1.6, n.s.). The mean performance of the eight experts was deemed suitable as a revised proficiency level for each task. Using objective performance metrics, all nine exercises demonstrated construct validity. Workload was similar between experts and novices and frustration was low for both groups. These data suggest that the nine structured exercises are suitable for proficiency-based robotic training.

The influence of seat backrest angle on human performance during whole-body vibration

This study investigated the effects of reclined backrest angles on cognitive and psycho-motor tasks during exposure to vertical whole-body vibration. Twenty participants were each exposed to three test stimuli of vertical vibration: 2–8 Hz; 8–14 Hz and 14–20 Hz, plus a stationary control condition whilst seated on a vibration platform at five backrest angles: 0° (recumbent, supine) to 90° (upright). The vibration magnitude was 2.0 ms−2 root-mean-square. The participants were seated at one of the backrest angles and exposed to each of the three vibration stimuli while performing a tracking and choice reaction time tasks; then they completed the NASA-TLX workload scales. Apart from 22.5° seat backrest angle for the tracking task, backrest angle did not adversely affect the performance during vibration. However, participants required increased effort to maintain performance during vibration relative to the stationary condition. These results suggest that undertaking tasks in an environment with vibration could increase workload and risk earlier onset of fatigue. Practitioner Summary Current vibration standards provide guidance for assessing exposures for seated, standing and recumbent positions, but not for semi-recumbent postures. This paper reports new experimental data systematically investigating the effect of backrest angle on human performance. It demonstrates how workload is elevated with whole-body vibration, without getting affected by backrest angle.

Work hours, workload, sleep and fatigue in Australian Rail Industry employees

Research suggests that less than 5 h sleep in the 24 h prior to work and/or more than 16 h of wakefulness can significantly increase the likelihood of fatigue-related impairment and error at work. Studies have also shown exponential safety declines with time on shift, with roughly double the likelihood of accident or injury after 10 h relative to the first 8 h. While it is acknowledged that reduced sleep, increased wakefulness and longer work hours produce work-related fatigue, few studies have examined the impact of workload on this relationship. Studies in the rail industry have focused on drivers. This study investigated fatigue in a large sample of Australian Rail Industry Employees. Participants were from four companies ( n = 90: 85m, 5f; mean age 40.2 ± 8.6 y). Data was analysed for a total of 713 shifts. Subjects wore wrist actigraphs and completed sleep and work diaries for 14-days. They also completed the Samn–Perelli Fatigue Scale at the beginning and end of shifts, and the NASA-TLX workload scale at least twice during each shift. Average (±SD) sleep length (7.2 ± 2.6 h), prior wake at shift end (12.0 ± 4.7 h), shift duration (8.0 ± 1.3) and fatigue (4.1 ± 1.3, “a little tired, less than fresh”) were within limits generally considered acceptable from a fatigue perspective. However, participants received 5 h or less sleep in the prior 24 h on 13%, were awake for at least 16 h at the end of 16% and worked at least 10 h on 7% of shifts. Subjects reported that they felt “extremely tired, very difficult to concentrate,” or “completely exhausted, unable to function effectively” on 13% of shifts. Sleep length (OR = 0.88, p < 0.01), shift duration (OR = 1.18, p < 0.05), night shift (REF = morning shift, OR = 2.12, p < 0.05) and workload ratings (OR = 1.2, p < 0.05) were significant predictors of ratings of extreme tiredness/exhaustion (yes/no). While on average, sleep loss, extended wakefulness, longer work hours and work-related fatigue do not appear problematic in this sample, there is still a notable percentage of shifts that are likely to be associated with high levels of work-related fatigue. Given the size of the Australian Rail Industry, with thousands of shifts occurring each day, this is potentially of operational concern. Further, results indicate that, in addition to sleep length, wakefulness and work hours, workload significantly influences fatigue. This has possible implications for bio-mathematical predictions of fatigue and for fatigue management more generally.

소음이 과제수행에 미치는 영향에 관한 연구

The purpose of this Study is to confirm the impact of noise on subject accomplishment as well as physical/mental load, and evaluates the effects of noise-masking and earplug. 15 college students participate in the test, and the comparison is performed by executing four projects according to conditional categories of noise environments; control condition, noise condition, earplug condition, and noise-masking condition. Noise in the field site of the H manufacrurer was used as the noise source, the general job aptitude test which consist of linguistic ability, math ability, perception ability, reasoning ability was used as the task of this project. To estimate physical/mental load evaluation, we uesd the heart rate R-R interval, Criteria flicker fusion freguency(CFF) and measured NASA-TLX workload for subjective evaluation. As the research outcome, it is shown that there is a meaningnd difference for the project task score, dropping rate of CFF, the heart rate, and NASA-TLX subjective evaluation score according to conditions of noise environment. Therefore, the impact of noise on capability of subject accomplishment as well as physical/mental load was confimled along with the effects of using earplug and noise-masking.

Evaluation of reaction time performance and subjective workload during whole-body vibration exposure while seated in upright and twisted postures with and without armrests

There is little knowledge on performance during vibration exposure combined with occupational hazards such as bent or twisted postures. In addition, little information is available on the effective use of armrests during performance-related tasks. This paper investigates the influence of sitting in different working postures on the reaction time and perceived workload of subjects exposed to whole-body vibration. Twenty-one subjects were exposed to 1–20 Hz random vibration in the vertical and fore-and-aft directions. A choice reaction time task was completed while seated in four posture conditions: upright or twisted, with and without armrests. Following the task, participants completed the NASA TLX workload assessment. Posture combined with whole-body vibration exposure had a significant influence on the ability to perform the task. The combined environmental stressors significantly degraded the performance; not only did their reaction times become compromised, the participants’ workload demand also increased. The most severe decrement in performance and workload was experienced while seated in a twisted posture with no armrest support. The inclusion of armrests significantly improved the participants’ ability to complete the task with a lower workload demand. Relevance to industry Twisted postures have been observed in a variety of machine operations and it is important to determine their influence on operator workload. Many off-road machines have suspension seats fitted with armrests; this paper demonstrates that armrest support provides additional benefits for off-road machine operators under combined environmental stressors.

Exploratory study of fatigue in light and short haul transport drivers in NSW, Australia

This exploratory study sought to identify relationships between work characteristics and fatigue experiences among light and short haul road transport drivers. Surveys were distributed to drivers of light goods vehicles (≤12 t gross vehicle mass) undertaking short haul work (within a 100 km radius of base) in seven geographical regions of NSW, Australia. The participating drivers ( n = 321) reported a range of freight tasks. They typically worked a 50-h, 5-day week primarily as day shifts, and spent just over half of their work time driving. Despite the predominance of regular, day work, 38% of participants experienced fatigue at least once a week while driving for work and 45% had nodded off while driving during the preceding 12 months. Stepwise logistic regression analysis revealed that longer daily work hours, higher subjective work demands, as measured by the NASA TLX workload scale, and the percentage of freight movements undertaken from customers to depots each explained unique variance in the frequency of fatigue experiences. The results of the study suggest that fatigue is an issue for some light and short haul road transport drivers and identifies work characteristics that should be investigated further.

Contextual Control Modes During an Airline Rescheduling Task

Tasks in complex, dynamic environments typically require many activities, including information seeking, communicating, coordinating, judging, decision making, and implementing decisions. In this paper, we examine how humans choose and organize these activities using a range of contextual control modes (CCMs) as described by Hollnagel: strategic, tactical, opportunistic, and scrambled. These CCMs are viewed as responses to contextual features, such as time limits and task demand. We specifically examine contextual control modes during an airline schedule adherence task and evaluate potential measures of these tasks in a controlled experiment using student participants. In the first portion of the experiment, we varied the time limits and in the second, we introduced a sudden increase in task demand. Information-seeking behaviors and participant solutions were recorded. NASA TLX workload ratings and participant self-assessments of contextual control mode were assessed. Participants reported operating in and transitioning between different contextual control modes in response to time limits and task changes. CCMs did not correlate with TLX ratings of demand and effort but did correlate with TLX-frustration and TLX-performance ratings and with time limits. The results suggest that high performance may be achieved in different contextual control modes and that the design of support systems should aim to support multiple modes.

Contextual Control Modes during an Airline Rescheduling Task

Tasks in complex, dynamic environments typically require many activities including information seeking, communicating, coordinating, judging, decision making, and implementing decisions. This paper examines how humans organize their actions, viewed as a form of control, by analyzing the selection of contextual control modes during an airline schedule adherence task. The experiment varied time limits and introduced a sudden change in the task during the last run. After each run, participants recorded their solution, NASA TLX workload ratings, and self-assessment of contextual control mode. Participants reported operating in, and transitioning between, different contextual control modes in response to time limits. Contextual control modes did not correlate with performance or TLX ratings of demand and effort but did correlate with time limit, TLX-frustration and TLX-performance ratings. The results suggest that high performance may be achieved through different contextual control modes and imply that decision aids should support multiple modes.