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Browsing by Author "Barfield, Woodrow S."

Now showing 1 - 19 of 19
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    Adult-child Differences in Spatial Learning in an Immersive Virtual Environment as a Function of Field-of-view
    McCreary, Faith Anne (Virginia Tech, 1997-10-03)
    Despite the potential of immersive virtual environments (VEs) as educational tools, little is known about how VE system parameters impact a child using the environment. Designers of VE applications targeted at children must rely on studies done with adults to guide their design decisions. The failure to understand how children differ from adults in their responses to VEs poses a serious obstacle to the design of effective learning environments for children. The main goal of this research was to quantify the impact of varying one VE system parameter, field-of-view, on large-scale, spatial learning in middle elementary schoolchildren and the incidence of side-effects in that population in an immersive VE. The other goals of this research were to identify 1) how, and if, middle elementary schoolchildren's responses to this environment differ from that of adult participants, and 2) how, and if, gender changed participant performance and responses. Adults and 7-9 year old children were taught a U-shaped route through a six room virtual house, while wearing a helmet mounted display (HMD). Participants viewed the environment under monoscopic conditions with the horizontal field-of-view (HFOV) of the display set at either 30 or 48 degrees. Head tracking was not enabled as the children were unable to maintain a normal head position while wearing the HMD. After the learning period, participants performed tasks designed to assess spatial knowledge of the space: 1) locomotion efficiency was measured by the number of collisions with objects, 2) landmark knowledge was measured by the participant's ability to recognize photos of objects found in the environment 3) route knowledge was measured by the participant's ability to correctly re-trace the route and name the sequence of landmarks along the route, 4) configuration knowledge was measured by the participant's ability to point to occluded landmarks, make spatial inferences, and construct a model of the environment. Participants also completed a simple questionnaire which assessed the incidence of equipment difficulties and side-effects, general enjoyment, and the sense of presence in the VE. Additionally, the participant's vision and balance was checked before and after immersion in the VE. Locomotion, route knowledge, and configuration knowledge efficiency increased significantly with both age and FOV. At the smaller FOV, both adults and 7-9 year olds developed a significantly lesser degree of spatial knowledge, with the effect being amplified in the 7-9 year olds. In general, the more sophisticated the level the spatial knowledge required by a task, the greater the impact of FOV and age, with configuration knowledge being achieved significantly less frequently than route knowledge. Gender also significantly impacted the development of configuration knowledge. Only landmark knowledge did not change with age, FOV, or gender. Also, the incidence of VE balance side-effects decreased significantly with age and was impacted by gender. The incidence of equipment difficulties also decreased with age,with significantly more, and longer, breaks being taken by 7-9 year olds than by adults. Further, general enjoyment of VE immersion and presence decreased significantly with age.
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    Analysis of Performance Resulting from the Design of Selected Hand-Held Input Control Devices and Visual Displays
    Spencer, Ronald Allen (Virginia Tech, 2000-08-18)
    Since the introduction of graphical user interfaces (GUI), input control devices have become an integral part of desktop computing. When interfacing with GUIs, these input control devices have become the human's primary means of communicating with the computer. Although there have been a number of experiments conducted on pointing devices for desktop machine, there is little research on pointing devices for wearable computer technology. This is surprising because pointing devices are a major component of a wearable computer system, allowing the wearer to select and manipulate objects on the screen. The design of these pointing devices will have a major impact on the ease with which the operator can interact with information being displayed (Card, English, and Burr, 1978). As a result, this research is the first in a series to investigate design considerations for pointing devices and visual displays that will support wearable computer users. Twenty soldiers participated in an experiment using target acquisition software with five pointing devices and two visual displays. The findings of the research strongly support the use of a relative mode-pointing device with rotational characteristics (i.e. trackball or thumbwheel) over other designs. Furthermore, the results also suggest that there is little difference between pointing devices operated with the thumb and index finger for target acquisition tasks. This study has also showed that there were little differences in pointing and homing time for pointing devices across the two visual displays. Finally, the study demonstrated that the Fitts' law model could be applied to hand-operated pointing devices for wearable computers. This is important because it allows the future development of pointing devices to be compared with the devices tested in this research using the Fitts' Law Index of Performance calculations.
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    Analysis of the Effects of Privacy Filter Use on Horizontal Deviations in Posture of VDT Operators
    Probst, George T. (Virginia Tech, 2000-06-06)
    The visual display terminal (VDT) is an integral part of the modern office. An issue of concern associated with the use of the VDT is maintaining privacy of on-screen materials. Privacy filters are products designed to restrict the viewing angle to documents displayed on a VDT, so that the on-screen material is not visible to persons other than the VDT operator. Privacy filters restrict the viewing angle either by diffraction or diffusion of the light emitted from the VDT. Constrained posture is a human factors engineering problem that has been associated with VDT use. The purpose of this research was to evaluate whether the use of privacy filters affected: 1) the restriction of postures associated with VDT use, 2) operator performance, and 3) subjective ratings of display issues, posture, and performance. Nine participants performed three types of tasks: word processing, data entry, and Web browsing. Each task was performed under three filter conditions: no filter, diffraction filter, and diffusion filter. Participants were videotaped during the tasks using a camera mounted above the VDT workstation. The videotape was analyzed and horizontal head deviation was measured at 50 randomly selected points during each task. Horizontal head deviation was measured as the angle between an absolute reference line, which bisects the center of the VDT screen, and a reference point located at the center of the participant's head. Standard deviation of head deviation were evaluated across filter type and task type. Accuracy- and/or time-based measures were used to evaluate performance within each task. Participants used a seven-point scale to rate the following: readability, image quality, brightness, glare, posture restriction, performance, and discomfort. The results indicated that the interaction between task and filter type affected the standard deviation of horizontal head deviation (a measure of the average range of horizontal deviation). The standard deviation of horizontal deviation was significantly larger within the Web browsing task under the no filter and diffusion filter conditions as compared to the diffraction filter condition. Filter type affected subjective ratings of the following: readability, image quality, brightness, posture restriction, and discomfort. The diffraction filter resulted in lower readability, image quality, and brightness ratings than the diffusion and no filter conditions. Participants reported that the ability to change postures was significantly decreased by the use of the diffraction filter as compared to the no filter and diffraction filter conditions. The diffraction filter resulted in an increase in reported discomfort as compared to the no filter condition. The interaction between filter and task type affected subjective ratings of performance. Participants reported a decrease in the rating of perceived performance under the diffraction filter / Web browsing condition as compared to the no filter / word processing, diffusion filter / Web browsing, and diffusion filter / data entry conditions. A decrease in the rating of perceived performance was reported in the diffraction filter / data entry condition as compared to the no filter / word processing and diffusion filter / Web browsing conditions. Neither diffraction nor diffusion filter affected performance within any of the tasks, based on the objective performance measures used in the experiment.
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    An Assessment of the Attention Demand Associated with the Processing of Information for In-Vehicle Information Systems (IVIS)
    Gallagher, John Paul (Virginia Tech, 2001-04-25)
    Technological interventions are being considered to alleviate congestion and to improve the quality of driving on our nation's highways. These new technology interventions will be capable of increasing the amount of information provided to the driver; therefore, steps must be taken to ensure they do not require a high attention demand. (Limited attention resources can be diverted from the primary task of driving to a secondary in-vehicle task). The attention demand required as part of the process of extracting information has been studied relatively extensively. However, the processing required to make complex decisions is not well understood and provides cause for concern. This study investigated the attention demand required to perform several types of tasks, such as selecting a route, selecting the cheapest route, and selecting the fastest route. The three objectives of this study were: 1) To investigate driver performance during IVIS tasks that required additional processing of information after the extraction of information from a visual display. 2) To develop a method for evaluating driver performance with regard to safety. This task was accomplished by performing an extensive review of the literature, and developing two composite measures. 3) To provide descriptive data on the proportion of drivers who exceeded a threshold of driver performance for each of the different IVIS tasks. An instrumented vehicle, equipped with cameras and sensors, was used to investigate on-road driver behavior on a four-lane divided road with good visibility. A confederate vehicle was driven in front of the instrumented vehicle to create a vehicle following situation. Thirty-six drivers participated in this study. Age, presentation format, information density, and type of task were the independent variables used in this study. Results from this study indicate that a high proportion of drivers' will have substantially degraded performance performing IVIS tasks such as selecting a route or a hotel from several possibilities. Findings also indicate that tasks involving computations, such as selecting the quickest or cheapest route, require a high attention demand and consequently should not be performed by a driver when the vehicle is in motion. In addition, text-based messages in paragraph format should not be presented to the driver while the vehicle is in motion. The graphic icon format should be utilized for route planning tasks.
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    Auditory-Based Supplemental Information Processing Demand Effects on Driving Performance
    Biever, Wayne Joseph (Virginia Tech, 1999-06-13)
    Thirty-six drivers of both genders from three different age groups performed auditory cognitive tasks while driving an instrumented vehicle. The tasks were of two types. The first type of task was the selection of a driving route from a list presented as a recorded sound. These tasks represented the use of In-Vehicle Information Systems (IVIS). The second type of task consisted of a conversation like series of questions designed to replicate the use of a cellular telephone while driving. The IVIS tasks consisted of two levels of information density (short-term memory load) and four element types (complexity levels) including listening, interpretation, planning, and computation. The effects of age, information density, and element type on driving performance were assessed using a composite set of performance measures. Primary measures of driving performance included lateral tracking, longitudinal control and eye glances. Secondary task performance was assessed by task completion time, skipped tasks and task errors. Additionally, subjective assessment was done using a situational awareness probe question and a modified NASA-TLX question set. Results showed that drivers demonstrated a general decrease in their ability to maintain their lateral position with increased task complexity. Additionally, speed and following distance were less stable during tasks. During tasks, drivers glanced less at their mirrors and instruments and left their lane more often than during baseline driving periods. Even during difficult tasks, drivers had high self-confidence in their awareness of surroundings. One result of particular interest was an increase in lane deviations and headway variance coupled with increased forward eye glance durations. It is believed that this is evidence of a condition called "Cognitive Capture" in which a driver, though looking more extensively at the forward roadway, is having difficulty tracking the lead vehicle and lane position. High cognitive load is causing the driver to disregard or shed visual information to allow processing of auditory task-related information. Another result of concern is the inability of drivers to assess their own impairment while performing in vehicle tasks. During tasks drivers demonstrated reduced scanning of mirrors and vehicle instrumentation. This clearly demonstrates reduced situational awareness. Additionally, during tasks lane tracking and headway maintenance performance decreased as well. However, during all tasks drivers assessed their workload higher than baseline driving even though they rated it near the bottom of the scale. Also, drivers perceived no decrease in their situational awareness. The results of this study show that driving performance can be negatively impacted by even fairly simple cognitive tasks while a driver is looking at the road with their hands on the wheel. Even while viewing the road, a driver may perform an auditory task and be cognitively overloaded to the point of safety concerns. An additional concern is that drivers underestimate the degree of their cognitive load and its impact on their driving performance.
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    Collaborative task performance for learning using a virtual environment
    Bystrom, Karl-Erik; Barfield, Woodrow S. (MIT Press, 1999-08-01)
    This paper describes a study on the sense of presence and task performance in a virtual environment as affected by copresence (one subject working alone versus two subjects working as partners), level of control (control of movement and control of navigation through the virtual environment), and head tracking. Twenty subjects navigated through six versions of a virtual environment and were asked to identify changes in locations of objects within the environment. After each trial, subjects completed a questionnaire designed to assess their level of presence within the virtual environment. Results indicated that collaboration did not increase the sense of presence in the virtual environment, but did improve the quality of the experience in the virtual environment. Level of control did not affect the sense of presence, but subjects did prefer to control both movement and navigation. Head tracking did not affect the sense of presence, but did contribute to the spatial realism of the virtual environment. Task performance was affected by the presence of another individual, by head tracking, and by level of control, with subjects performing significantly more poorly when they were both alone and without control and head tracking. In addition, a factor analysis indicated that questions designed to assess the subjects' experience in the virtual environment could be grouped into three factors: (1) presence in the virtual environment, (2) quality of the virtual environment, and (3) task difficulty.
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    A conceptual model of the sense of presence in virtual environments
    Bystrom, Karl-Erik; Barfield, Woodrow S.; Hendrix, Claudia (MIT Press, 1999-04-01)
    This paper proposes a model of interaction in virtual environments which we term the immersion, presence, performance (IPP) model. This model is based on previous models of immersion and presence proposed by Barfield and colleagues and Slater and colleagues. The IPP model describes the authors' current conceptualization of the effects of display technology, task demands, and attentional resource allocation on immersion, presence, and performance in virtual environments. The IPP model may be useful for developing a theoretical framework for research on presence and for interpreting the results of empirical studies on the sense of presence in virtual environments. The model may also be of interest to designers of virtual environments.
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    The Effect of Communication Style on Task Performance and Mental Workload Using Wearable Computers
    Nash, Eric B. (Virginia Tech, 2000-08-10)
    This thesis measured the mental workload associated with operating a voice activated software application run on wearable computer under five different communication styles (buttons, command line, icon buttons, icon text menus, and text menus). The goal of this thesis was to determine which communication style would be best allow wearable computer users to simultaneously perform other non-computer tasks. Thirty subjects were randomly assigned to using one of five software versions (n = 6), each of which utilized a unique communication style. The mental workload associated with operating each version was assessed by monitoring the performance of secondary tasks. Secondary tasks consisted of completing a block assembly, digit subtraction, and walking along a marked pathway. Each secondary task was performed twice by itself and once while operating one of the software versions, creating a total of nine trials per subject. Block assembly task performance measures included average assembly time, percentage correct blocks, and percentage correct blocks attempted. Digit subtraction measures included percentage of correct digits. And path walking measures included average walking speed. Subjective estimates of mental workload were also collected for those trials in which subjects operated the wearable computer and performed physical tasks using the NASA Task Load Index (TLX). Finally, usability information was collected for each software version via a questionnaire form. Each of the five versions of the experimental software application was operationally identical to the others, but utilized a separate communication style. The button version displayed available functions via sets of labeled buttons in the control screen. The icon button version replaced the appearance of these buttons with labeled icons. The text menu version displayed available functions textually via a pull down main menu. The icon text version displayed appended icons to the left of each main menu item. Finally, the command line version displayed no labels, buttons, menus, or icons for any functions. The experimental software was designed as a day planner/scheduling application used to set reminder dates on a calendar, edit task lists, and edit phone listings. Under the multiple resource view of mental workload, it was hypothesized that the different versions and secondary tasks would demand distinct types of mental resource and, consequently, that mental workload would be observed as lowest when the version and secondary task demanded different types of mental resources. In contrast, it was also hypothesized that mental workload would be observed as highest when the version and secondary task demanded the same type of mental resources. Although separate one way ANOVAs performed on all secondary task measures failed to indicate statistically significant differences in mental workload across the versions, secondary task performance was consistently observed as best for subjects using the icon button version. Analysis of NASA TLX subscale data indicated that the block assembly task was rated as requiring less effort and the digit task rated as requiring less mental demand when the icon button version was used. These results generally support using an icon button communication style for wearable computer software applications. Results of this study are applicable to the design of the user interface of wearable computers. These results not only report subjective and objective measures for assessing the amount of mental effort associated with operating a wearable computer and performing various physical tasks simultaneously, but also provide estimates for determining the amount of physical task performance decrement to expect when wearable computer are also operated. Such data may be used to determine human factors guidelines for matching wearable computer interfaces to physical tasks so that interference between the two is minimal.
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    Effects of stereopsis and head tracking on performance using desktop virtual environment displays
    Barfield, Woodrow S.; Hendrix, Claudia; Bystrom, Karl-Erik (MIT Press, 1999-04-01)
    This study investigated performance in a desktop virtual environment as a function of stereopsis and head tracking. Ten subjects traced a computer-generated wire using a virtual stylus that was slaved to the position of a real-world stylus tracked with a 6-DOF position sensor. The objective of the task was to keep the virtual stylus centered on the wire. Measures collected as the subjects performed the task were performance time, and number of times the stylus overstepped the virtual wire. The time to complete the wire-tracing task was significantly reduced by the addition of stereopsis, but was not affected by the presence of head tracking. The number of times the virtual stylus overstepped the wire was significantly reduced when head-tracking cues were available, but was not affected by the presence of stereoscopic cues. Implications of the results for performance using desktop virtual environments are discussed.
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    Effects of Technological Support on Decision Making Performance of Distributed Groups
    Cano, Arnoldo Rafael (Virginia Tech, 1997-12-12)
    This research was concerned with the collection of empirical data necessary to estimate the effects of decision support tools on the performance of distributed groups. Data was collected in a controlled experimental environment that simulated a geographically-dispersed meeting through the use of videoconferencing and group communication support (GCSS) technology. Results of the use of a Group Decision Support System (GDSS) on group process and outcome variables were mixed. As predicted by the literature the use of a GDSS by distributed groups improved overall group consensus, decision accuracy, and decision effectiveness. The use of a GDSS also increased perceived process structure. Contrary to previous studies, the use of a GDSS increased decision time, and decreased overall satisfaction with the group process. No significant effects were found for perceived consensus, cooperation, amount of information exchange, or confidence in the decision. A strong correlation was found between decision quality and decision time. An even stronger correlation was found between perceived structure of the process and satisfaction with the process. The lack of feedback about the process and its outcomes could explain the lack of a GDSS effect on perceptions of consensus, cooperation, and confidence in the decision. Perception of subjective measures of the process may depend on the presence of the appropriate types of feedback. The results suggest that an increase in structure without a perceived improvement in decision quality (confidence in the decision) tends to reduce group satisfaction. A richer taxonomy for Computer Supported Cooperative Work (CSCW) systems is proposed whereby three orthogonal dimensions of group support are defined. These three dimensions of group support are: Communication support, decision support, and presence support. This new taxonomy suggests a number of research directions aimed at the empirical identification of contextual and design factors relevant to distributed group performance and decision making performance in general.
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    Evaluating the Effectiveness of Augmented Reality and Wearable Computing for a Manufacturing Assembly Task
    Baird, Kevin Michael (Virginia Tech, 1999-06-21)
    The focus of this research was to examine how effectively augmented reality (AR) displays, generated with a wearable computer, could be used for aiding an operator performing a manufacturing assembly task. The research concentrated on comparing two technologies for generating augmented reality displays (opaque vs. see-through), with two current types of assembly instructions (a traditional assembly instruction manual vs. computer aided instruction). The study was used to evaluate the effectiveness of the wearable based augmented reality compared to traditional instruction methods, and was also used to compare two types of AR displays in the context of an assembly task. For the experiment, 15 subjects were asked to assemble a computer motherboard using the four types of instruction: paper manual, computer aided, an opaque AR display, and a see-through AR display. The study was run as a within subjects design, where subjects were randomly assigned the order of instruction media. For the AR conditions, the augmented environments were generated with a wearable computer, and viewed through two types of monocular, head-mounted displays (HMD). The first type of HMD was a monocular opaque HMD, and the second was a monocular see-though HMD. Prior to the experiment, all subjects performed a brief training session teaching them how to insert the various components of the motherboard in their respective slots. The time of assembly and assembly errors were measured for each type of media, and a questionnaire was administered to each subject at the end of each condition, and at the end of the experiment to determine the usability of the four instructional media. The results of the experiment indicated that both augmented reality conditions were more effective instructional aids for the assembly task than either the paper instruction manual or the computer aided instruction. The see-through HMD resulted in the fastest assembly times followed by the opaque HMD, the computer aided instruction, and the paper instructions respectively. In addition, subjects made fewer errors using the AR conditions compared to the other two types of instructional media. However, while the two AR conditions were a more effective instructional media when time was the response measure, there were still some important usability issues associated with the AR technology that were not present in the non-AR conditions. Many of the subjects indicated that both types of HMDs were uncomfortable, and over half expressed concerns about poor image contrast with the see-through HMDs. Finally, this thesis discusses the results of this study as well as implications for the design and use of AR and wearable computers for manufacturing assembly tasks.
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    The Impact of Local/Short Haul Operations on Driver Fatigue
    Hanowski, Richard J. (Virginia Tech, 2000-05-23)
    Massie, Blower, and Campbell (1997) indicate that trucks that operate less than 50 miles from the vehicle's home base comprise 58% of the trucking industry. However, despite being the largest segment, research involving local/short haul (L/SH) operations has been scant. In fact, little is known about the general safety issues in L/SH operations. As a precursor to the present research, Hanowski, Wierwille, Gellatly, Early, and Dingus (1998) conducted a series of focus groups in which L/SH drivers provided their perspective on safety issues, including fatigue, in their industry. As a follow-up to the Hanowski et al. work, the effort presented here consisted of an on-road field study where L/SH trucks were instrumented with data collection equipment. Two L/SH trucking companies and 42 L/SH drivers participated in this research. To the author's knowledge, this is the first in-situ data collection effort of its kind with L/SH drivers. The analyses focused on determining if fatigue is an issue in L/SH operations. Of primary interest were critical incidents (near-crashes) where drivers were judged to be at fault. The results of the analyses indicated that fatigue was present immediately prior to driver involvement in at-fault critical incidents. Though it is difficult to determine why fatigue was present, the results seem to indicate that much of the fatigue that the drivers' experienced was brought with them to the job, rather than being caused by the job. There are four basic outputs of the Phase II research: (1) a description of the L/SH drivers who participated, (2) a description of critical incidents, (3) a determination if fatigue is an issue in L/SH trucking, and (4) the validation of the fatigue factors cited in Hanowski et al. (1998) using a proposed fatigue model. These four outputs culminate in a set of pragmatic guidelines to address fatigue and other safety issues in L/SH operations. Five guidelines are proposed that are directed at: (1) driver education with regard to on-the-job drowsiness/inattention, (2) driver education with regard to sleep hygiene, (3) driver training, particularly for novice L/SH truck drivers, (4) driver screening, and (5) public monitoring of L/SH driver performance.
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    Integral Perception in Augmented Reality
    McGee, Michael K. (Virginia Tech, 1999-09-24)
    Augmented reality, the superimposing of graphics or text onto an actual visual scene, is intended to enhance a user's understanding of the real world. This research examines the perceptual, cognitive, and human factors implications of combining integrally designed computer-generated imagery with real world scenes. Three experiments were conducted to test the theoretical and practical consequences of integral perception in augmented reality. The first experiment was a psychophysical study that had participants subjectively assess the integrality of 32 scenes comprising four different augmented reality object environments (computer, brain, text, and liquid dynamic model), projected at two transparency levels (opaque, and semi-transparent), and presented with four different graphic textures (color, grayscale, white, and wireframe). The second experiment expanded the psychophysical integrality assessment of augmented scenes to 32 different images composed of four new environments (housing development, computer lab, planetary photo, and trees in countryside), with multiple computer-generated graphics (two, four, six, and eight), at two levels of integrality as defined by experiment one (high, low). The third experiment was an applied study that had two phases: 1) learning tasks using three augmented environments; and, 2) assembly tasks using eight augmented video instructions. The computer-generated graphics for each phase of experiment three were presented at two levels of integrality (high, low) as defined by experiment one. The primary results of the three experiments show that augmented reality scenes with computer-generated imagery presented transparently and in color were perceived most integrally; increasing the number of graphics from two to eight decreased integral perception; and, high integral graphics aided performance in learning and real assembly tasks. From the statistical results and experimenter observation of the three experiments, guidelines for designing integrally perceived graphics in augmented environments were compiled based on principles of human factors, perception, and graphic design. The key themes of the design guidelines were: 1) maintaining true shape information in the computer-generated graphics 2) using highly realistic graphics for naturalistic augmented settings; 3) considering the hardware limitations of the augmented system, particularly the display; and, 4) designing appropriately for the task (simple, complex, hands-on, cognitive, dynamic, static, etc.).
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    An Investigation of Collision Avoidance Warnings on Brake Response Times of Commercial Motor Vehicle Drivers
    Shutko, John (Virginia Tech, 1999-04-30)
    The goal of this experiment was to determine what if any effect two different types of warnings have the brake reaction time of distracted commercial motor vehicle operators. The warning conditions were: No Warning, Auditory Tire Skid Warning, and One Second Brake Pulse Warning. Each participant was distracted via a distracter task during the experiment. As the participants were distracted, an obstacle was launched out into their forward path. Each participant received his/her appropriate warning, according to what condition they were placed, when the obstacle entered their headway. It was determined that the Auditory Tire Skid Warning aided in decreasing the movement times, while the One Second Brake Pulse Warning aided in decreasing the number of collisions with the barrels and speed at contact with the barrels.
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    Measurement of Driver Preferences and Intervention Responses as Influenced by Adaptive Cruise Control Deceleration Characteristics
    McLaughlin, Shane Brendan (Virginia Tech, 1998-04-10)
    In comparison to conventional cruise control, adaptive cruise control (ACC) vehicles are capable of sensing forward traffic and slowing to accommodate as necessary. When no forward vehicles are present, ACC function is the same as conventional cruise control. However, with ACC, when a slower vehicle is detected, the ACC system will decelerate and follow at a selected time-based distance. While slowing to follow, the driver will experience a system-controlled deceleration of the ACC vehicle. An experiment was conducted to evaluate driver preferences for the distance at which the primary deceleration occurs and the level of deceleration that is obtained. Driver intervention was required in one trial and driver response behavior was measured. Ten men and ten women in two age groups evaluated the decelerations from a cruise speed of 70mph to a following speed of 55mph behind a confederate lead vehicle on the highway. Evaluations can be made using four scales: Good vs. Bad, Comfortable vs. Uncomfortable, Jerky vs. Smooth, and Early vs. Late. Decelerations of approximately 0.06g which occur approximately 200ft to 250ft behind the lead vehicle were most preferred. Prior to intervention, foot position ranged from a point directly below the brake pedal to 16.4in from the brake pedal. Foot motion began between 21.12s time-to-collision (TTC) and 3.97s TTC. Eighty percent of the participants paused to "cover" the brake before final motion to activate the brake. The older age group intervened (braked) later than the younger age group. Driver braking after intervention ranged from 0.16g to 0.32g.
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    On-Road Investigation of Fluorescent Sign Colors to Improve Conspicuity
    Anders, Richard Lee (Virginia Tech, 2000-08-09)
    This thesis documents Phase III of a research program undertaken by the Virginia Transportation Research Council and the Virginia Tech Transportation Institute in cooperation with the 3M Company and the Virginia Department of Transportation for the evaluation of visual performance of retroreflective signs of various color combinations. Phase I was an off-road field experiment conducted to determine the best sign color combination, letter stroke width, and letter size for the emergency sign. Based upon the results of Phase I, three color combinations were chosen for testing (black on coral, black on light blue, and yellow on purple) against a baseline color combination of black on orange.Phase II was conducted using an instrumented vehicle through a construction zone-related detour. Questionnaire data were also obtained. The independent variables of interest were sign color combination, age, and visibility condition. The findings of Phase II indicated that use of a color combination other than the traditional black on orange sign would improve driver performance and safety when used for trailblazing during critical incidents, especially when the incident route overlaps a work zone detour. A serious limitation of Phases I and II is that the use of fluorescent colors was not evaluated. Anecdotal evidence suggests that the use of fluorescent colors on signs improves their conspicuity. The purpose of Phase III was to evaluate fluorescent sign color combinations for incident management trailblazing purposes. This study consisted of an on-road investigation using an instrumented vehicle over a 12.2-mile route in urban and rural areas of Montgomery County, Virginia. The following conclusions were made:*A non-fluorescent yellow on non-fluorescent purple sign is least preferred by both older and younger drivers when compared to the other sign color combinations employed in this study.*Both younger and older drivers have a preference for a black on fluorescent yellow-green sign.* Fewer late braking maneuvers and fewer turn errors were recorded during daytime conditions than during nighttime conditions. *Older drivers tended to register more late braking maneuvers than did younger drivers.
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    Performance and Usability of Force Feedback and Auditory Substitutions in a Virtual Environment Manipulation Task
    Edwards, Gregory W. (Virginia Tech, 2000-11-03)
    Recent technology developments have made possible the creation of several commercial devices and a selected number of development platforms for the inclusion of haptics (the sense of touch) in virtual environments (VE). This thesis sought to investigate and develop a better understanding of whether or not haptics or sound substitutions improved manipulation performance or usability in VE applications. Twenty-four volunteers (12 males and 12 females) participated in a 2 (haptics) x 2 (sound) x 2 (gender) mixed factorial experiment in which they completed a VE manipulation task involving the assembly and disassembly of 5 interconnecting parts. Performance for the manipulation task was measured through completion time and the number of collisions made, as well as subjective measures of usability. Results indicated that completion times were slower and collision counts were higher for males with the addition of haptics (ptime = 0.03; pcollisions<0.05), while females exhibited a smaller increase in collision counts and no increase in completion time with the addition of haptics. Nonetheless, there were improved usability attributes when haptics were incorporated, more specifically, an increased sense of realism, perceived helpfulness and perceived utility in a design task (p<0.05 for all). Sound was found to be an effective substitute for haptics in most measures taken while the combination of sound and haptics versus either alone, did not demonstrate any signs of improving performance or any usability attributes. It is therefore recommended that sound substitution be used in VE manipulation tasks where the extra haptic information is desired, and minimizing completion time or collisions are the overall goal. Finally, for the utility of the feedback towards a design task, users ranked haptics as being more useful than sound, but ranked the combination of sound and haptics as being the best feedback condition (p<0.05). Further research is required to determine whether this belief is consistent with objective measures.
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    Peripheral Dynamic Visual Acuity Under Randomized Tracking Task Difficulty, Target Velocities, and Direction of Target Presentation
    Holland, Dwight (Virginia Tech, 2000-01-17)
    Dynamic Visual Acuity (DVA) in the visual periphery has not been extensively studied. DVA is a measure of an observer's ability to resolve critical details in a target when there is relative motion between the target and the observer. This dissertation examined static and dynamic acuity in the 25-55 deg region of retinal eccentricity under a variety of conditions. Functionally, this region of the visual field is just beyond the "blind spot," but not yet in the "far" visual periphery of 60-90 deg of eccentricity. Traditionally, DVA research has been confined to the assessment of DVA for the foveal (or "central") visual system. However, the peripheral (or "ambient") visual system provides very important information content for the visual and neuro-vestibular systems. This peripheral visual information content is also used to create a sense of ego motion (termed "vection"), and for alerting the visual system to targets entering or leaving the field of view. Past findings involving visual acuity in the peripheral retina have demonstrated that peripheral acuity performance has components related to the notion of "attention" as well. This is particularly true if the peripheral vision research results are to be applied to visually and attentionally complex and/or dynamic real-world environments. In this experiment, the 25-55 deg eccentric region of the retina was tested for DVA in 50 observers. This study used a mixed four-factor research design with Eccentricity (25, 35, 45, 50, 55 deg) as a between-subjects factor. Tracking Difficulty (monitor only, easiest, moderate, most difficult tracking levels), Landolt C Target Velocities (0.0, 4.88, 14.62, and 24.40 deg/s), and Target Direction ("F/R:" fixed or random direction of target appearance) were used as within-subjects factors. A computer presented the Landolt C ring targets under the stated conditions in a random fashion. Acuity was determined for each trial by a modified descending method-of-limits approach with the Landolt C ring target gap widths utilized as the determinant for the acuity measure. The Tracking Task was designated as the primary task, with the secondary task being to indirectly observe the orientation (up, down, right, left) of the Landolt C rings being presented under the various conditions of Target Velocity and Target Direction in the retinal periphery. The resulting Analysis of Variance (ANOVA) revealed significant differences (p < 0.05) for each of the main effects of Eccentricity, Tracking Task Difficulty, Velocity, and Target Direction (F/R). Only two of the two-way interactions were found to be significant (p < 0.05)-- those of Tracking Difficulty x Target Velocity and Target Velocity x Target Direction interactions. The results are discussed in terms of the psychophysical, attention, and "tunnel vision" like models of peripheral visual performance, along with other related human factors literature in the domain of "situation awareness" that are relevant to this general problem area. The results of a separate follow-on mini-study are discussed using a Two-way Contingency Table analysis across all of the treatment conditions when verbal intrusion was embedded in the previously described experimental conditions. This mini-study revealed a significant association (p < 0.05) with not seeing the peripheral targets as accurately when intrusion was present, versus when there was no verbal intrusion. This effect was more pronounced at the highest velocities (14.62 and 24.40 deg/s) as compared with the slower ones (0 and 4.88 deg/s) in terms of the strength of the association, as assessed by a Kappa test statistic. Taken all together, and with consideration given to the relatable scientific literature, these results indicate that the more "busy" a person is with cognitive, visual, or motor-skills tasks, the more likely an individual will show degradation in static or dynamic peripheral visual acuity tasks. Peripheral vision often serves as a "warning" or "status" sensory modality for what is occurring in the local task environment, separate from the foveal visual system. Future research is suggested given the sensitivity of the peripheral visual system to these factors, particularly with regard to how factors involving the notion of attention may affect such "peripheral visual awareness" issues. These issues in turn may play an important role from a human factors and safety perspective in a variety of person-rated vehicular domains. Specific areas that are highlighted for future research in the domain of attention and "peripheral visual awareness" include the low-altitude high-performance flying realm, the flying environment more generally, and in other dynamic multi-task vehicular environments such as that encountered while simultaneously driving and using a car cellular phone.
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    Quantifying the Participatory Ergonomic Effects of Training and a Work Analysis Tool on Operator Performance and Well-Being
    Saleem, Jason Jamil (Virginia Tech, 1999-11-11)
    Participatory ergonomics (PE) is a macroergonomics approach in which the end-users actively participate in developing and implementing the technology. PE can be an effective method for involving front-line workers in analyzing and redesigning their own jobs. PE can be used at the macro-level, the micro-level, or somewhere in between. At the macro-level, the focus of the PE program is across an entire organization or work system. At the micro-level, the focus of a PE approach is on a particular task, workstation, or product. A major benefit for using PE is that workers are more likely to accept changes to their job if they participate in the redesign. Furthermore, workers' motivation, job satisfaction, and knowledge are enhanced through the participatory process. There are many case studies that describe successful PE approaches. These studies, however, lack a control group or comparison group and so changes in the workplace (e.g., a reduction of musculoskeletal injury) cannot be attributed directly to the interventions resulting from the PE program with certainty. Quantifying the effects of PE is difficult because of problems in trying to isolate variables. Confounding variables are often difficult to contain. This study quantified some of the effects of PE by utilizing a controlled experimental design in the laboratory in which participants analyzed and redesigned a manual material handling job. The effects of this PE approach were quantified by measuring a reduction of risk factors associated with the job and by measuring a lift index of the lifting task that indicates a risk for injury. Many authors state or infer that some degree of ergonomics training should be given to the participants in a PE approach. However, the effects of providing ergonomics training to participants in these types of participatory approaches are unclear. This research evaluates the effects of providing the participants with basic ergonomics instruction relevant to the job being evaluated and redesigned. Also, this research suggests if the NIOSH lifting equation can be an effective tool in a participatory ergonomics approach in the redesign of a manual material handling job that involves lifting tasks. A 2-factor, between-subjects design was used. Participants consisted of 32 volunteers (16 males and 16 females). Only individuals that have had no prior ergonomics knowledge were considered for the subject pool. Participants performed a simulated manual material handling job in the laboratory. After performing the job, some subjects were given ergonomics training and/or instructed on how to use the NIOSH lifting equation for manual lifting tasks. The participants were then asked to redesign the original job. The participants' redesigns were compared to the redesigns of the control subjects (who received no ergonomics instruction and did not use the NIOSH lifting equation). The subjects who received the ergonomics instruction identified significantly more risk factors in the original job and eliminated significantly more risk factors in the redesign than the control subjects. The subjects who learned and used the NIOSH lifting equation also identified significantly more risk factors in the original job but did not eliminate significantly more risk factors in the redesign. The subjects who received the ergonomics instruction and who used the NIOSH lifting equation were not shown to have an advantage over the subjects who received the ergonomics instruction alone. The group that received the ergonomics training performed optimally with respect to the other experimental groups. Implications for participatory ergonomics approaches are discussed.