Physical workload of lorry drivers: a comparison of four methods of transport

Abstract

Four groups of eight lorry drivers, transporting goods on wheeled cages, as packed goods, on pallets, or as bulk cargo, were studied during a complete working day. The drivers working with bulk cargo served as a reference group. Manual materials handling and the working postures were studied by observation. The heart rate (HR) was continuously recorded and related to observed tasks. The relationship between HR and oxygen uptake during a simulation of loading and unloading and the maximal oxygen uptake ([Vdot]O2 max) were measured in a laboratory for every driver. The lorry drivers worked long hours, only the group transporting wheeled cages worked less than 11 hd^-1 on average. Driving made up almost half of the total working time in all groups. In general, the highest HR was found during loading and unloading. Loading and unloading of wheeled cages was done for 2nd^-1, at 50% of [Vdot]O2max. The drivers transporting packed goods and pallets loaded and unloaded for around 100mind^-1, at 48% and 35% of [Vdot]O2 max respectively. When the drivers of these two groups lifted, their trunks were flexed for more than 60% of the time. The most important difference between the reference group and the other groups was that the drivers of the former rarely pushed or pulled anything. It is suggested that the required pushing and pulling forces were largely responsible for the high physical workload during loading and unloading.     

Recovering articulated pose: a comparison of two pre and postimposed constraint methods

We contrast the performance of two methods of imposing constraints during the tracking of articulated objects, the first method preimposing the kinematic constraints during tracking and, thus, using the minimum degrees of freedom, and the second imposing constraints after tracking and, hence, using the maximum. Despite their very different formulations, the methods recover the same pose change. Further comparisons are drawn in terms of computational speed and algorithmic simplicity and robustness, and it is the last area which is the most telling. The results suggest that using built-in constraints is well-suited to tracking individual articulated objects, whereas applying constraints afterward is most suited to problems involving contact and breakage between articulated (or rigid) objects, where the ability to test tracking performance quickly with constraints turned on or off is desirable.     

A comparison of two hierarchical optimization methods

In this note the interaction prediction method and the goal coordination method for the multi-level optimization of large-scale interconnected dynamical systems with separable quadratic coat functions and linear dynamics are compared. The vehicle for the comparison is a twelth-order complex counter-current example taken from the literature. The computational load for the two methods is compared qualitatively whereas the convergence characteristics arc tested on the example. A simple condition is also given for the convergence of the interaction prediction method. This is also tested on the example.     

Speed choice by drivers: The issue of driving too slowly

Quite correctly, the majority of road safety speeding initiatives focus on drivers travelling at excessive speeds. This study, however, focused on the potential problem of driving too slowly. Six thousand, four hundred and eighty vehicles from around the Perth metropolitan area in Western Australia had their speeds recorded; observations were also made of these vehicles to identify characteristics of the driver and vehicle. In addition, a community survey with 240 members of the public was conducted to examine their attitudes towards slow drivers. As expected, results showed that older drivers drove more slowly than the other age brackets, women drove more slowly than men, and that heavily laden vehicles drove more slowly than other types of vehicles. Additionally, the slowest days were weekdays and the quickest were Saturdays. Community attitudes, generally mirrored the observational findings, and indicated that the public believed that slow driving was sometimes a safety problem causing some accidents. These data are discussed, and some possible countermeasures are briefly introduced to address the problem.     

Speed choice by drivers: the issue of driving too slowly

Quite correctly, the majority of road safety speeding initiatives focus on drivers travelling at excessive speeds. This study, however, focused on the potential problem of driving too slowly. Six thousand, four hundred and eighty vehicles from around the Perth metropolitan area in Western Australia had their speeds recorded; observations were also made of these vehicles to identify characteristics of the driver and vehicle. In addition, a community survey with 240 members of the public was conducted to examine their attitudes towards slow drivers. As expected, results showed that older drivers drove more slowly than the other age brackets, women drove more slowly than men, and that heavily laden vehicles drove more slowly than other types of vehicles. Additionally, the slowest days were weekdays and the quickest were Saturdays. Community attitudes, generally mirrored the observational findings, and indicated that the public believed that slow driving was sometimes a safety problem causing some accidents. These data are discussed, and some possible countermeasures are briefly introduced to address the problem.     

Perceptual processes used by drivers during overtaking in a driving simulator

This study investigated the control strategies and decision making of drivers who were executing overtaking maneuvers in a fixed-base driving simulator. It was found that drivers were frequently inaccurate in deciding whether it was safe to overtake in front of an oncoming vehicle. One source of error in this situation was the control strategy adopted by the driver; in several instances our drivers initiated an overtaking maneuver when the oncoming car's distance was above a critical value, even though there was not sufficient time to complete a safe maneuver. Adaptation to closing speed (produced by driving on a straight open road) also had large effects on overtaking behavior. For all participants, closing speed adaptation resulted in decisions that were delayed, of higher risk, and more variable. Actual or potential applications of this research include improved training for younger drivers and the development of in-car interfaces that reduce closing speed adaptation.     

A comparison of two parametric surface patch methods

The Bézier and Ferguson methods of representing surfaces are compared. Although there are very clear differences in their mode of use they are closely similar in their mathematical basis.     

两种倍频方式的比较与设计研究

针对倍频电路进行了研究与设计。分别使用硬件倍频和FPGA倍频两种方式实现了对50Hz方波的两倍频,并对两种方式进行了比较研究。     

Learner outcomes and satisfaction: A comparison of live video-streamed instruction,satellite broadcast instruction,and face-to-face instruction

This study examined the final grade and satisfaction level differences among students taking specific courses using three different methods: face-to-face in class, via satellite broadcasting at remote sites, and via live video-streaming at home or at work. In each case, the same course was taught by the same instructor in all three delivery methods, and an attempt was made to survey students taking the course via the three different delivery methods. MANOVA results indicated no grade or satisfaction level differences among the three populations. Self-reported computer literacy skills revealed a slight fit between the chosen delivery mode and the reported computer literacy skills. These results provide additional evidence to support both the “no significant difference” phenomenon and the use of distance education as a viable, convenient and flexible alternative delivery mode capable of extending learning opportunities to non-traditional students.     

Facing drift: a comparison of three methods

Drift is a common phenomenon in active sensors and, if left untreated, is generally the limiting factor in their performance. It is shown that drift and spread in sensor characteristics are tightly interwoven due to finite sensitivity to biasing parameters. Modern treatments of drift are dynamical under operating conditions, notably so chopping, the sensitivity variation method and the recently introduced van Putten-method. These methods differ in regards to drift-dependence on biasing. In their application to silicon flow sensors, the first two reduce but do not eliminate drift. The geometric van Putten-method leaves biasing invariant, which eliminates drift and obtains uniform sensor-characteristics leaving drift-free operation.     

Perception-response speed and driving capabilities of brain-damaged and older drivers

Three experiments including reaction time (RT) tasks and driving tasks were conducted to identify variables that may be sensitive to the effects of brain damage or aging and to determine how RT tasks relate to driving performance. In Experiment 1 mean RTs of the brain-damaged and older subjects disproportionately increased relative to those of controls, with increasing difference between subsequent compound stimuli. In Experiment 2 response accuracy of brain-damaged subjects deteriorated more than that of controls when the similarity of a task to actual driving increased. In Experiment 3 brain-damaged patients were slower and less accurate than the controls on all measures of a platoon car-following task, whereas the older subjects were only less accurate. Compared with those of the controls, brake RTs of neither the older subjects nor the patients were disproportionately affected by increasing task load. Performance on the platoon driving task could be successfully predicted by a laboratory RT task on time estimation only for the brain-damaged subjects.     

A comparison of two sampling methods for global sensitivity analysis

We compare the convergence properties of two different quasi-random sampling designs – Sobol?s quasi-Monte Carlo, and Latin supercube sampling in variance-based global sensitivity analysis. We use the non-monotonic V-function of Sobol? as base case-study, and compare the performance of both sampling strategies at increasing sample size and dimensionality against analytical values. The results indicate that in almost all cases investigated here, the Sobol? design performs better. This, coupled with the fact that effective Latin supercube sampling requires a priori knowledge of the interaction properties of the function, leads us to recommend Sobol? sampling in most practical cases.     

A comparison of two optimization methods for mesh quality improvement

We compare inexact Newton and block coordinate descent optimization methods for improving the quality of a mesh by repositioning the vertices, where the overall quality is measured by the harmonic mean of the mean-ratio metric. The effects of problem size, element size heterogeneity, and various vertex displacement schemes on the performance of these algorithms are assessed for a series of tetrahedral meshes.

Design and development of a technology enhanced hybrid instruction based on MOLTA model: Its effectiveness in comparison to traditional instruction

Using the model for learning and teaching activities (MOLTA), a new technology enhanced hybrid instruction was designed, developed and implemented. The effectiveness of the hybrid instruction in regard to students’ achievement, knowledge retention, attitudes towards the subject, and course satisfaction was evaluated in comparison to traditional classroom instruction. Experimental study with pre-test, post-test control group design was carried out. The sample of the study consisted of 50 university students enrolled in “Computer Networks and Communication” course. The control and experimental groups composed of 24 and 26 students respectively, and the experiment lasted 14 weeks. The findings of the study indicated no significant difference between the hybrid course and the traditional course in students’ achievement, knowledge retention, satisfaction, and attitude.     

Lateral control assistance for car drivers: a comparison of motor priming and warning systems

OBJECTIVE: This paper's first objective is to determine whether motor priming assistance (consisting of directional steering wheel vibrations) can be of some benefit compared with more traditional auditory (lateralized sound) or vibratory (symmetric steering wheel oscillation) warning devices. We hypothesize that warning devices favor driving situation diagnosis, whereas motor priming can improve the initiation of action even further. Another objective is to assess the possible benefits of using multimodal information by combining auditory warning with simple steering wheel vibration or motor priming. BACKGROUND: Within the context of active safety devices, the experiment dealt with moderately intrusive driving assistance devices that intervene when a certain level of risk in terms of lane departure is reached. METHOD: An analysis of the steering behavior of 20 participants following episodes of visual occlusion was carried out. Five warning and motor priming devices were compared. RESULTS: All tested devices improved the drivers' steering performance, although their effects were modulated by the drivers' risk assessment. However, performance improvements were found to be greater with a motor priming device. No additional performance enhancement was observed when auditory warning was added to steering wheel vibration or motor priming devices. CONCLUSION: This study confirms the hypothesis that the direct intervention of motor priming at the action level is more effective than a simple warning, which intervenes upstream in situation diagnosis. Multimodal information did not seem to improve driver performance. APPLICATION: This study proposes a new kind of lateral control assistance, which acts at a sensorimotor level, in contrast with traditional warning devices.     

Haptic recognition of shapes at different scales: A comparison of two methods of interaction

In order to design a “haptic zoom”, in this fundamental study, we compare two scaling methods by focusing on the strategies adopted by subjects who are using a sensory substitution device. Method 1 consists of a reduction of the sensor size and of its displacement speed. Speed reduction is obtained by a “human” movement adjustment (hand speed reduction). Method 2 consists of a straightforward increase in the dimensions of the image. The experimental device used couples a pen on a graphics tablet with tactile sensory stimulators. These are activated when the sensor impinges on the outline of the figure on the computer screen. This virtual sensor (a square matrix composed of 16 elementary fields) moves when the pen, guided by human hand movements, moves on the graphics tablet. The results show that the recognition rate is closely dependent on the size of the figure, and that the strategies used by the subjects are more suitable for method 2 than for method 1. In fact, half of the subjects found that method 1 inhibited their movements, and the majority of them did not feel the scaling effect, whereas this was clearly felt in method 2.     

A comparison of two training methods for improving warning symbol comprehension

This study compared the effectiveness of two different types of training in improving comprehension of warning symbols by younger (aged 20-35 years) and older adults (aged 50-70 years). The verbal label training paired the symbol with a label describing its meaning while the accident scenario training further expanded on the nature of the hazard, the required/prohibited actions, as well as the possible consequences of failing to comply. Contrary to prior research (e.g., [Lesch, M.F., 2003. Comprehension and memory for warning symbols: age-related differences and impact of training. J. Safety Res. 34, 495-505]), there was no difference in comprehension for younger and older adults prior to training, with both groups only obtaining about 40% correct responses. Both types of training improved performance on a subsequent comprehension test. However, the accident scenario training produced a higher percentage of correct responses, greater confidence in those responses, as well as a longer-lasting reduction of reaction times. In order to further improve symbol design, as well as training to address comprehension difficulties, future research should more closely examine symbol characteristics that influence comprehension.