The visual and driving performance of monocular and binocular heavy-duty truck drivers

This study compared the performance of 40 monocular and 40 binocular tractor-trailer drivers on measures of both visual and driving performance. On the visual measures, the mononuclear drivers were significantly deficient in contrast sensitivity, visual acuity under low illumination and glare, and binocular depth perception. They were not significantly deficient in static or dynamic visual acuity, visual field of individual eyes, or glare recovery. Driving measures of visual search, lane keeping, clearance judgment, gap judgment, hazard detection, and information recognition showed no differences between monocular and binocular drivers. Monocular drives were poorer than binocular drivers only in sign reading distance in both daytime and nighttime driving. This decrement correlated significantly with the binocular depth perception measure. There were large individual differences within each group for most of the visual and driving performance measures. It was concluded that monocular drivers have some significant reductions in selected visual capabilities and in certain driving functions dependent on these abilities, compared with binocular drivers. However, monocular drivers are not significantly worse than binocular drivers in the safety of most day-to-day driving functions. Implications of these findings and the large individual differences within each group are discussed.     

A Search Performance Test for Visual Lobe Size

Visual search is a very common form of inspection and monitoring activity. This paper reviews work by the author that demonstrates a relationship between visual lobe size and search performance. A card sorting task was found to correlate significantly with visual lobe dimensions and it is suggested that this relationship may be used as the basis of a test for screening individuals for certain types of inspection and monitoring activities. The test is considered to be a more useful measure of visual scanning ability than tests of foveal acuity.     

显示移动速度对动态搜索绩效的影响研究

为了探究动态视觉搜索任务中显示移动速度对搜索绩效的影响，设计了动态视觉搜索实验。通过E-prime软件测试8个显示移动速度下的搜索绩效，并对反应时间进行配对t检验。实验结果表明：当显示移动速度不高于4°/s时，动态搜索绩效与静态搜索绩效没有显著差异；当显示移动速度不低于6°/s时，二者差异显著，且其差异随显示移动速度的增大而增大。此外，当显示移动速度不高于8°/s时，不同显示移动速度之间的搜索绩效差异性与速度区间的宽度Δω有关，Δω越大，搜索绩效差异越显著；当显示移动速度高于8°/s时，不同显示移动速度之间的动态搜索绩效均存在显著差异。动态视觉搜索任务的平均反应时间和误检率随着显示移动速度的增大而增大。研究结果说明显示移动速度对动态搜索绩效的影响显著，可为动态界面显示移动速度的设置提供一定参考。     

A comparison of static and dynamic hazard perception tests

Hazard perception is a vital component to safe driving and hazard perception tests (HPTs) are being used with greater frequency for driver training, assessment and licensure. In this study, we compared a dynamic HPT (Scialfa et al., 2011), which presents short video scenes to observers and a static HPT (Scialfa et al., 2012), which uses still images. Both tests require the observer to indicate the presence of a traffic conflict that would lead to a collision between the “camera” vehicle and another road user or fixed object. Young adult drivers (n = 56) completed both forms of the HPT, along with a modified version of the Driver Behavior Questionnaire ( Reason et al., 1990) and a measure of simple reaction time. Self-reported collision and moving violation data were also collected. As in previous work, both static and dynamic HPTs had good reliability. The correlation between composite static and dynamic scores was approximately .40, but was reduced to approximately .25 when simple reaction time was controlled. Both HPTs predicted lapses and errors on the Driver Behavior Questionnaire, but neither predicted self-reported collisions or moving violations. Discussion focuses on the differences in visual cues available in dynamic and static scenes and how these differences could influence decisions about potential hazards.     

Optimum speed of visual inspection using a systematic search strategy

In an earlier paper, the authors presented models of human functioning in visual inspection and derived optimal working speeds to balance the cost of time and the cost of errors. Both self-paced and externally paced models assumed a random search strategy. It was noted that choosing a standard speed for visual inspection is difficult with standard work measurement techniques and that the data required for the suggested search model are easily measurable. The purpose of this paper is to complement the earlier work by deriving similar models employing a systematic search strategy. The two models can be considered as bounds on actual performance; thus the current paper complements the previous one by establishing an upper bound rather than a lower bound on performance in search tasks. Comparisons between the two strategies are presented.     

Cognitive and visual predictors of UFOV performance in older adults

Eighty two community dwelling older adults (52 females) aged 62–92 years (mean = 75) completed a battery of cognitive and visual tests selected to assess functions relevant to driving performance. These were visual acuity, contrast sensitivity, general mental competence (Mini Mental State Examination, MMSE), processing speed (Inspection Time, IT), crowding across the visual field (Proficiency of Peripheral Vision Processing, ProPerVis) and change detection (DriverScan). These six tasks provided predictor variables for performance on the Useful Field of View test (UFOV), a well validated test of fitness to drive that includes subtests for (i) processing speed; (ii) divided attention; and (iii) selective attention. Relative importance regression analyses confirmed that UFOV is sensitive to attentional and speed processes but suggested that subtest (i) primarily reflects visual acuity and contrast sensitivity; subtest (ii) is better explained by change detection and processing speed; and subtest (iii) predominantly reflects crowding and contrast sensitivity. Unexpectedly, given no evidence of substantial cognitive decline, MMSE contributed significantly to performance on the more complex subtests (ii) and (iii).     

The Utility of Signal-Detection Theory in the Analysis of Industrial Inspector Accuracy

In an experimental study of inspector accuracy utilizing industrial electronics inspectors as subjects, a visual, subject-paced task requiring a “yes-no” response was used. The results are thought to be generally applicable to visual inspection tasks, but may not be applicable in an inspection task requiring measurement, as in machine parts inspection. The major conclusion of the research is that signal-detection measures are more useful in performance evaluation than are other available measures, because they not only relate performance to payoff, but indicate the magnitude and direction of improvement required.     

Theoretical issues in the design of visual inspection systems

The objective of this review essay is to both chronicle and analyse literature in the area of visual inspection. Classical as well as contemporary papers are included to describe both the historical development and the state of the art of visual inspection theories and technologies. Human operators, despite well-documented problems, often perform visual inspection. While supervized machine systems obviate some of the problems associated with human inspectors, other problems still exist. In particular, accounting for a supervisor's perception of a machine's performance (as gauged, e.g. by trust) and consequent actions. The difficulties associated with these two alternatives have led to the emergence of a third alternative: collaborative human/machine or hybrid systems, which combine the advantages of both alternatives—in theory. However, in practice, how to best distribute the functions between a human and machine, in a dynamic environment in real time, is problematic. Moreover, a human's perceptions of its counterpart's performance remain an issue. These unresolved problems are subjects for future research. In the interim, the alternatives are critiqued to create a basis for establishing guidelines to select the alternative that is best suited for a given situation.     

Impact resistance of fiber reinforced wet-mix shotcrete Part 2: plate tests

In Part 1 of this paper, data on impact resistance of fiber reinforced wet-mix shotcrete obtained by testing beam specimens was presented. Ten different types of commercially available fibers were investigated. It was argued that since shotcrete in many applications is loaded dynamically, slow-rate static tests are not sufficient for a comprehensive characterization of its in-place performance. mance. It was also demonstrated that shotcrete is a highly stress-rate sensitive material, and its performance under impact is very different from that predicted by the slow-rate, quasi-static tests. From a standardization point of view, proper characterization of toughness and energy absorption capability of fiber reinforced shotcrete remains a challenge before the industry. Both beam and plate specimens are prescribed, but little understanding exists of the correlation, if any, between these two specimen geometries. In this paper, the same ten fiber types, tested in Part 1 using beam specimen, were investigated using plate specimens. As before, both static and impact tests were performed. Plate tests showed similar toughness enhancement due to fiber reinforcement, but the relative improvements between fiber types are not necessarily in agrcement with those indicated in the beam tests. Plate specimens were also found be less sensitive to changes in the rate of loading from static to dynamic. Considering these issues, and realizing that in practice shotcrete is often loaded in bi-axial bending, the use of plate specimens rather than beam specimens for the characterization of toughness of fiber reinforced shotcrete is recommended.     

Characterization of unidirectional carbon fibre reinforced plastic laminates

The purpose of the present paper is to outline a set of recommended tests in order to characterize the behavior of carbon fibre reinforced plastic laminates. The tests outlined in this contribution are classification of visual defects, dimension and density, fibre and resin content, tensible strength, apparent interlaminar shear strength, in-plane shear modulus, dynamic torsion property, static bending property, dynamic bending property, and thermal expansion coefficient. As a selected example, results of two tensile tests on CFRP laminates are reported.     

EPO材料缓冲性能的探究

目的通过试验对比EPE,EPS,EPO等3种材料缓冲性能的优劣。方法对一定规格的3种材料试样进行静态压缩试验、动态压缩试验,并结合Ansys有限元仿真技术,进行数据处理分析。结果在静态缓冲特性试验中,当材料所受应力大于3.5 kPa且小于180 kPa时,EPO与EPE及EPS的静态缓冲性能系数大小关系为EPEEPOEPS;当应力小于3.5 kPa或者大于180 kPa时,EPO的静态缓冲系数最小,即此时EPO的静态缓冲性能优于EPE和EPS。从动态缓冲特性试验中可知,静应力小于10 kPa时,3种材料的缓冲性能大小为EPSEPOEPE;当静应力大于14kPa时,缓冲性能大小排序为EPSEPOEPE;静应力大小介于10 kPa和14 kPa之间时,3种材料具有相似的缓冲效果。EPO材料动态缓冲特性处于EPE以及EPS之间,当静应力较大时,EPO呈现出与EPE更相近的性能,缓冲性能较EPS有所提升。结论经测试比较,EPO材料具有较好的缓冲性能,某些环境下可以作为新缓冲包装材料使用,未来有较好的发展前景。     

The effect of manufacturing processes on the fatigue lifetime of aeronautical bolts

Many aeronautical fastners are exposed to cyclic stresses during service. Therefore, such parts are usually designed for limited fatigue lifetime. Various combinations of process type and sequence may be employed to produce threads, each resulting in different fatigue properties. Specifications of aircraft bolts often require production of threads by heat treatment followed by rolling, in order to improve the fatigue properties. Unfortunately, these specifications are not always followed to the letter. Therefore, for either quality assurance or failure analysis purposes, it is important to be able to determine unambigiously the process by which threads were produced. The objectives of this work were to study the effect of varied thread manufacturing process type and sequence on the mechanical properties of AISI 4340 stud bolts, and to develop a laboratory procedure for distinguishing between them. Threads were produced on heat-treated and non-heat-treated stud bolts either by machining or cold-rolling. The non-heat-treated bolts were subsequently heat-treated. All bolts were then subjected to mechanical testing (static tensile, dynamic fatigue, hardness and microhardness tests), metallographic and fractographic examinations. While the fatigue properties were significantly affected by the manufacturing process used, no effects on the tensile strength of the bolt were observed. Metallographic inspection and microhardness testing, but not fractographic inspection, were found to be effective for distinguishing between different manufacturing procedures.     

不同年龄段人群的动态有效视野研究

探究年龄对动态有效视野特征变化的影响。采用动态视觉搜索任务,共测试样本138人。研究结果表明,年龄对动态有效视野特性具有显著影响,随着年龄增加,有效视野面积、有效视野周长和形状因子随之下降;视野特性受凝视点移动速度影响,随着速度增加,视野范围有缩小且视野形状偏离圆形的趋势。本文的研究可为针对不同年龄段人群设计动态视觉搜索任务提供指导。     

Optimal and heuristic inspection schedules for multistage production systems

Consider a single inspection facility that can be quickly switched among multiple inspection tasks. It can be used (for example) for detecting malfunction (or down state) production stages in a multistage production system. We assume that a properly working (or up state) production stage moves to a down state in any period with fixed probability. The stage then stays down until it is inspected and immediately restored back to an up state. Our purpose is to schedule inspections among the different production stages so as to maximize the fraction of good items produced. An optimal inspection schedule for a two stage production system is provided. For the general case of more than two stages, four heuristics are compared. We conclude that the proposed dynamic schedule is easy to derive, always feasible, and outperforms the static schedules.     

Consistent Identification of CFRP Viscoelastic Models from Creep to Dynamic Loadings

Rate‐dependent models require creep or mechanical tests at various strain rates in order to be identified and validated. Different geometries coexist for creep and static tests (normative geometry) and for dynamic tests. Therefore, due to geometrical sample considerations, experimental results could be inconsistent for identification or validation procedures, inducing, for example, differences on the shear modulus only due to the change of geometry. The objective of this work is to present an improved sample geometry that allows to obtain consistent mechanical tests results at various strain rates highlighting the rate dependencies of laminates. In particular, a complete mechanical validation of the sample geometry for dynamic tests is successfully performed in order to avoid inconsistency. Results of static and dynamic tests on the validated geometry are analysed, and the rate dependency of the elastic properties of the UD T700GC/M21 mesoscopic ply is highlighted on a wide strain rate range (10^?3 to 10² s^?1). Finally, the identification of a non‐linear viscoelastic model is performed on dynamic and creep tests results in order to obtain a representative model for dynamic, static and creep loadings, and to demonstrate the importance of introducing the improved geometry for the dynamic tests.     

Relationship between acuity for gratings and for tumbling-E letters in peripheral vision.

Earlier studies have reported that grating resolution is sampling-limited in peripheral vision but that letter acuity is generally poorer than grating acuity. These results suggest that peripheral resolution of objects with rich Fourier spectra may be limited by some factor other than neural sampling. To examine this suggestion we formulated and tested the hypothesis that letter acuity in the periphery is sampling-limited, just as it is for extended and truncated gratings. We tested this hypothesis with improved methodology to avoid the confounding factors of target similarity, alphabet size, individual variation, peripheral refractive error, and stimulus size. Acuity was measured for an orientation-discrimination task (horizontal versus vertical) for a three-bar resolution target and for a block-E letter in which all strokes have the same length. We confirmed previous reports in the literature that acuity for these targets is worse than for extended sinusoidal gratings. To account for these results quantitatively, we used difference-spectrum analysis to identify those frequency components of the targets that might form a basis for performing the visual discrimination task. We find that discrimination performance for the three-bar targets and the block-E letters can be accounted for by a sampling-limited model, provided that the limited number of cycles that are present in the characteristic frequency of the stimulus is taken into account. Quantitative differences in acuity for discriminating other letter pairs (e.g., right versus left letters E or characters with short central strokes) could not be attributed to undersampling of either the characteristic frequency or the frequency of maximum energy in the difference spectrum. These results suggest additional tests of the sampling theory of visual resolution, which are the subject of a companion paper.     

An on-road assessment of cognitive distraction: impacts on drivers' visual behavior and braking performance

In this on-road experiment, drivers performed demanding cognitive tasks while driving in city traffic. All task interactions were carried out in hands-free mode so that the 21 drivers were not required to take their visual attention away from the road or to manually interact with a device inside the vehicle. Visual behavior and vehicle control were assessed while they drove an 8 km city route under three conditions: no additional task, easy cognitive task and difficult cognitive task. Changes in visual behavior were most apparent when performance between the No Task and Difficult Task conditions were compared. When looking outside of the vehicle, drivers spent more time looking centrally ahead and spent less time looking to the areas in the periphery. Drivers also reduced their visual monitoring of the instruments and mirrors, with some drivers abandoning these tasks entirely. When approaching and driving through intersections, drivers made fewer inspection glances to traffic lights compared to the No Task condition and their scanning of intersection areas to the right was also reduced. Vehicle control was also affected; during the most difficult cognitive tasks there were more occurrences of hard braking. Although hands-free designs for telematics devices are intended to reduce or eliminate the distraction arising from manual operation of these units, the potential for cognitive distraction associated with their use must also be considered and appropriately assessed. These changes are captured in measures of drivers' visual behavior.     

Visual Inspection of Highway Bridges

The Federal Highway Administration recently conducted an investigation to assess the reliability of visual inspection of highway bridges as implemented by state departments of transportation. The study focused on routine and in-depth inspection, the two most prevalent forms of visual inspection of bridges. Because visual inspection is a highly subjective nondestructive evaluation technique, the results of these bridge inspections can be highly variable and are dependent on many factors. This study included the completion of 10 bridge inspection tasks by 49 practicing state bridge inspectors. With regard to routine inspections, this study showed that condition ratings are assigned with significant variability. Specifically, approximately 68% of condition ratings are within 1 rating point of the average. The results of the in-depth superstructure inspections indicated that these inspections are not likely to detect and identify the specific types of defects for which this inspection procedure is sometimes prescribed. Specifically, widespread defects such as those normally noted during a routine inspection are likely to be noted; however, local deficiencies, such as crack indications, are unlikely to be detected. The results of the deck delamination survey indicate that the accuracy of this type of inspection is relatively poor, with few inspection teams providing results that could be considered to accurately portray the condition of the deck.     

新型组合式道床系统静动态特性试验研究

对于一种新型组合式道床试验系统的结构,进行了静动态试验,研究组合式道床系统在承受大载荷作用下,钢轨以及道床板结构受力变化规律,并将静态试验数据与理论计算结果相互对比。在负载状态下对该系统进行了动态锤击试验,验证安装谐振浮轨减振扣件及道床隔振垫组合道床系统的总体减振效果。静态力学特性数据表明：谐振浮轨扣件及道床隔振垫组合式系统理论计算与实际实验值基本一致;动态试验结果得到该组合道床系统在实验室等效轴载14 t～16 t条件下20 Hz～200 Hz频率范围,平均减振量可达到25 dB。     

Testing assumptions implicit in the use of the 15-second rule as an early predictor of whether an in-vehicle device produces unacceptable levels of distraction

Given the proliferation of in-vehicle technologies, techniques must be developed to ensure devices do not produce unacceptable levels of distraction. One approach is to use static time on task (e.g., the 15-second rule). However, this practice makes three critical assumptions: (1) static time on task predicts time on task while driving; (2) time on task measured in a hazard-free environment predicts time on task when drivers expect hazards; (3) time on task predicts perceived distraction, collisions, and driving errors. To test these assumptions, two tasks were compared in 32 drivers using a driving simulator. The tasks were manipulating controls of a radio/tape deck and dialling a hand-held cellular phone. Static time on task underestimated dynamic time on task, though the differences between tasks were roughly consistent across testing conditions, with the cellular task taking more time. Participants who expected hazards required slightly more time on task than those who did not, but the effect was only marginal (p=0.09) and consistent across tasks. Finally, the device with higher static time on task also produced significantly more lane deviations and perceived interference, though the predicted pattern of results did not emerge for collisions and hazard response time.