Effects of physical workload on cognitive task performance and situation awareness

Sixteen participants performed a military operations simulation directing loading of helicopters to weight capacity within an allotted timeframe and subject to a set of decision rules. The participants stood, walked or jogged on a treadmill while performing the simulated cognitive task. Task performance was measured in terms of helicopter loading rate and accuracy. Situation awareness (SA) was measured using a simulation freeze technique and SA queries. Subjective workload was measured using the NASA-TLX. Results indicated a general trend of decreasing SA with increasing physical workload for perceptual knowledge, comprehension and overall SA. Results also revealed higher subjective workload during jogging than during the walking and standing conditions. However, the physical workload manipulations did not appear to affect cognitive task performance. This study has practical implications for defining physical and cognitive workloads in specific dynamic, complex work environments to support operator SA and performance.     

论事务性脑力劳动者工作量的测定

首先论述了在现代社会中确定脑力劳动者一天合理的工作量的必要性，然后对脑力劳动者按事务性和决策性进行了分类，最后介绍了几种确定事务性脑力劳动者工作量的方法及应用。     

对事务性脑力劳动的一种定量测量方法

确定脑力劳动者的工作量问题一直是工业工程师试图解决的问题。本文介绍了一种非常实用的定量确定脑力劳动工作量的方法，该方法曾在我国一大型企业应用，收到了比较好的效果。     

脑力负荷的预测与分析方法

随着计算机在现代系统中的广泛应用，系统操作人员已正在变成脑力工作者，在系统设计中预测这些操作人员的脑力负荷，以史脑力负荷过高而影响系统的业绩具有十分重要的意义。本文首先介绍了三种不同的脑力负荷预测和分析方法。最后提出了一个脑力负荷预测的基本模型。     

Speed choice and mental workload of elderly cyclists on e-bikes in simple and complex traffic situations: A field experiment

To study the speed choice and mental workload of elderly cyclists on electrical assisted bicycles (e-bikes) in simple and complex traffic situations compared to these on conventional bicycles, a field experiment was conducted using two instrumented bicycles. These bicycles were identical except for the electric pedal support system. Two groups were compared: elderly cyclists (65 years of age and older) and a reference group of cyclists in middle adulthood (between 30 and 45 years of age). Participants rode a fixed route with a length of approximately 3.5 km on both bicycles in counterbalanced order. The route consisted of secluded bicycle paths and roads in a residential area where cyclist have to share the road with motorized traffic. The straight sections on secluded bicycle paths were classified as simple traffic situations and the intersections in the residential area where participants had to turn left, as complex traffic situations. Speed and mental workload were measured. For the assessment of mental workload the peripheral detection task (PDT) was applied. In simple traffic situations the elderly cyclists rode an average 3.6 km/h faster on the e-bike than on the conventional bicycle. However, in complex traffic situations they rode an average only 1.7 km/h faster on the e-bike than on the conventional bicycle. Except for the fact that the cyclists in middle adulthood rode an average approximately 2.6 km/h faster on both bicycle types and in both traffic conditions, their speed patterns were very similar. The speed of the elderly cyclists on an e-bike was approximately the speed of the cyclists in middle adulthood on a conventional bicycle. For the elderly cyclist and the cyclists in middle adulthood, mental workload did not differ between bicycle type. For both groups, the mental workload was higher in complex traffic situations than in simple traffic situations. Mental workload of the elderly cyclists was somewhat higher than the mental workload of the cyclists in middle adulthood. The relatively high speed of the elderly cyclists on e-bikes in complex traffic situations and their relatively high mental workload in these situations may increase the accident risk of elderly cyclist when they ride on an e-bike.     

心理负荷多维主观评定的实验研究

本研究在总结前人成果的基础上将心理负荷主观反应归纳为“任务难度”等８个方面，并结合追踪作业负荷实际加以实验检验。通过敏感性分析和因素分析，作者最终提出“任务复杂性”、“任务压力”、“心理努力与疲劳”和“紧张水平”是主观心理负荷最重要的维度，建议设计多维主观评定量表时考虑这４个方面。     

时间长短对脑力负荷强度影响的研究

文章通过实验的方法探讨了工作时间长短对脑力负荷强度的影响。在实验中，被试者被要求做一项脑力要求非常高的工作，心算三位数乘一位数加四位数的算术。被试者被分为两组，一组必须在２０ｓ之内完成计算一道算术题，另一组计算时间不受限制，但一题算完下一题将马上出现。两组被试者都进行了一整天８ｈ的计算。实验结果表明，工作时间长短对脑力劳动负荷强度有一定的影响，但影响值比我们预计的要小得多。     

Mental workload when driving in a simulator: Effects of age and driving complexity

Driving errors for older drivers may result from a higher momentary mental workload resulting from complex driving situations, such as intersections. The present study examined if the mental workload of young and older active drivers vary with the difficulty of the driving context. We adopted the probe reaction time (RT) technique to measure the workload while driving in a simulator. The technique provided clear instructions about the primary (driving) and secondary (RT) tasks. To avoid structural interference, the secondary task consisted of responding as rapidly as possible with a vocal response (“top”) to an auditory stimulus. Participants drove through a continuous 26.4-km scenario including rural and urban sections and probes (stimuli) were given in a baseline static condition and in three different driving contexts embedded into the overall driving scenario. Specifically, stimuli were given randomly when (a) driving on straight roads at a constant speed, (b) approaching intersections for which the driver had to stop the car, and (c) when overtaking a slower vehicle. Unless a driving error was made, drivers did not need any emergency responses. Reaction time was defined as the temporal interval between the auditory stimulus and the onset of the corresponding verbal response detected from the analog signal of a piezo-electric microphone fixed on a headset (ms accuracy). Baseline RTs were similar for both groups. Both groups showed longer RTs when driving and RTs increased as the complexity of the driving contexts increased (driving straights, intersections, overtaking maneuvers). Compared to younger drivers, however, older drivers showed longer RTs for all driving contexts and the most complex driving context (overtaking maneuvers) yielded a disproportionate increase. In conclusion, driving leads to a greater mental workload for the older drivers than for the younger drivers and this effect was exacerbated by the more complex driving context (overtaking maneuvers).     

A simulator study of the effects of singing on driving performance

This study aimed to investigate how singing while driving affects driver performance. Twenty-one participants completed three trials of a simulated drive concurrently while performing a peripheral detection task (PDT); each trial was conducted either without music, with participants listening to music, or with participants singing along to music. It was hypothesised that driving performance and PDT response times would be impaired, and that driver subjective workload ratings would be higher, when participants were singing to music compared to when there was no music or when participants were listening to music. As expected, singing while driving was rated as more mentally demanding, and resulted in slower and more variable speeds, than driving without music. Listening to music was associated with the slowest speeds overall, and fewer lane excursions than the no music condition. Interestingly, both music conditions were associated with slower speed-adjusted PDT response times and significantly less deviation within the lane than was driving without music. Collectively, results suggest that singing while driving alters driving performance and impairs hazard perception while at the same time increasing subjective mental workload. However, singing while driving does not appear to affect driving performance more than simply listening to music. Further, drivers’ efforts to compensate for the increased mental workload associated with singing and listening to music by slowing down appear to be insufficient, as evidenced by relative increases in PDT response times in these two conditions compared to baseline.     

Monitoring drivers’ mental workload in driving simulators using physiological measures

Many traffic accidents are caused by, or at least related to, inadequate mental workload, when it is either too low (vigilance) or too high (stress). Creating variations in mental workload and accident-prone driving for research purposes is difficult in the real world. In driving simulators the measurement of driver mental workload is relatively easily conducted by means of physiological measures, although good research skills are required and it is time-consuming. The fact that modern driving simulator environments are laboratory-equivalent nowadays allows full control with respect to environmental conditions, scenarios and stimuli, and enables physiological measurement of parameters of mental workload such as heart rate and brain activity. Several examples are presented to illustrate the potential of modern high-standard driving simulator environments regarding the monitoring of drivers’ mental workload during task performance.     

Head-up displays assist helicopter pilots landing in degraded visual environments

Civilian rotary-wing aircraft pilots typically rely on visual information from the external environment to guide flight, but are increasingly required to operate in degraded visual environments. The current study evaluated the impact of a head-up display (HUD) upon pilot performance, perceived situation awareness and workload. A 2 × 2 repeated measures design required qualified rotary-wing pilots (N = 6) to fly in clear and degraded visual conditions both with and without the HUD. In degraded visual conditions, the HUD significantly improved pilot perceived situation awareness whilst simultaneously reducing workload. Objective flight technical performance data offered preliminary support for a positive change in pilot behaviour when using the HUD in degraded visual conditions.     

The consequences of an increase in heavy goods vehicles for passenger car drivers' mental workload and behaviour: a simulator study

The effects of an increase in Heavy Goods Vehicles (HGVs) on merging behaviour and on mental workload of motorists during filtering in and out of traffic were studied. Participants drove in a driving simulator in a total of 12 conditions; twice in each of two weather conditions and in three traffic conditions. The weather conditions were clear weather and foggy weather. The traffic conditions were without HGVs (i.e. only private cars), the current mix of HGVs and private cars, and a condition with a 70% increase of HGVs leading to an HGV column in the slow lane. The focus of the study was on assessing effects on behaviour and mental workload during filtering into traffic, and during exiting from the motorway. During the experiment driving performance was registered, behaviour was observed, self reports were collected, and the participant's heart rate was recorded. The results showed that directly after filtering into traffic the variation in driving speed increased and the minimum time headway decreased with an increase in the proportion of HGVs. Joining motorway traffic was considered to involve greater effort and risk in the condition with a column of HGVs. The effects of the conditions on heart rate are less clear, although the moment when the participants joined the traffic is clearly visible. The effects of weather conditions were limited, drivers adapting their driving behaviour in adverse weather by reducing speed. To exit the motorway is not a difficult manoeuvre. For that reason the lane change from the left hand to the right hand lane that preceded the exit was analysed. Although increased mental effort was reported and the lane change was visible in the heart rate record, no critical changes as a result of increase in proportion of HGVs were found for this manoeuvre. However, in the condition with a column of HGVs, the exit that had to be taken was most frequently missed as HGVs obstructed the view of the exit signs. It is concluded that an increase in HGVs will make merging into traffic more mentally demanding and will decrease safety margins.     

Differences of drivers' reaction times according to age and mental workload

This study was designed to examine differences in reaction times of drivers of various age groups and to assess the influence of mental workload on reaction times. Experiments were performed on a simulated street and under other conditions to identify drivers with long reaction times and drivers whose reaction times are affected strongly by mental workloads while driving on a public road. Reaction times after hearing a buzzer were measured under five conditions: (1) sitting in a stationary vehicle, (2) executing mental calculations in a stationary vehicle, (3) driving on a simulated street, (4) executing mental calculations while driving on a simulated street, and (5) driving on a public road. Subjects were 10 drivers each of three age groups. Each experiment was performed by these subjects under the five conditions. Results showed that mental calculations increased the average reaction time for each age group. Mental calculations increased differences among age groups and individuals, and increased differences in respective drivers' individual performance. Mental calculations influenced elderly drivers' reaction times remarkably. Results also demonstrated that an experiment on a simulated street identified drivers who showed long reaction times on a public road.     

无人机操作员态势感知的实验研究

通过对30名现役战士操作某型无人机仿真器与态势感知问卷调查相结合,对无人机操作员态势感知与工作负倚的关系进行了研究。实验结果表明：工作负荷越高,操作员态势感知能力越低;同工作负荷情况下,操作次数越多,操作员态势感知能力越高。     

Book review

Workload control (WLC) is a leading production planning and control (PPC) solution for small to medium sized enterprises (SMEs) and make-to-order (MTO) companies, but when WLC is implemented, practitioners find it difficult to determine suitable workload norms to obtain optimum performance. Theory has provided some solutions (e.g., based on linear programming) but, to remain optimal, these require the regular feedback of detailed information from the shop floor about the status of work-in-process (WIP), and are therefore often impractical. This paper seeks to predict workload norms without such feedback requirements, analysing the influence of shop floor characteristics on the workload norm. The shop parameters considered are flow characteristics (from an undirected pure job shop to a directed general flow shop), and the number of possible work centres in the routing of a job (i.e., the routing length). Using simulation and optimisation software, the workload norm resulting in optimum performance is determined for each work centre for two aggregate load-oriented WLC approaches: the classical and corrected load methods. Results suggest that the performance of the classical approach is heavily affected by shop floor characteristics but no direct relationship between the characteristics and norm to apply could be established. In contrast, results suggest that the performance of the corrected load approach is not influenced by shop floor characteristics and the workload norm which results in optimum performance is the same for all experiments. Given the changing nature of MTO production and the difficulties encountered with the classical approach, the corrected load approach is considered a better and more robust option for implementation in practice. Future simulations should investigate the influence of differing capacities across work centres on the workload norm while action research should be conducted to apply the findings in practice.     

情境意识理论在驾驶界面设计中的研究现状与展望

目的 针对列车驾驶自动化和智能化的发展带来驾驶界面信息量大增,司机工作转变为信息监控和决策后,带来的心理负荷明显上升且情境意识下降等问题,梳理情境意识理论在智能驾驶界面设计中的研究现状,并对下一步研究进行展望。方法 进行文献分析,整理情境意识理论的研究现状和进展,从情境意识与自动化驾驶界面设计、显控界面图文信息、工作负荷、自动化下的人机交互四个具有智能化驾驶界面显著特征的相关设计应用的研究入手,对相关研究成果进行了综述。结论 分析了目前的研究现状和发展方向,提出了应加强对智能化背景下司机的驾驶人机交互认知特征、驾驶情境意识的表现特征及视觉策略、基于情境意识增强的智能列车驾驶界面可视化设计方法等方面的研究。