Safety, Efficiency, and Mental Workload in Simulated Teledriving of a Vehicle as Functions of Camera Viewpoint.

Teleoperation services are expected to operate on-road and often in urban areas. In current teleoperation applications, teleoperators gain a higher viewpoint of the environment from a camera on the vehicle's roof. However, it is unclear how this viewpoint compares to a conventional viewpoint in terms of safety, efficiency, and mental workload. In the current study, teleoperators (n = 148) performed driving tasks in a simulated urban environment with a conventional viewpoint (i.e., the simulated camera was positioned inside the vehicle at the height of a driver's eyes) and a higher viewpoint (the simulated camera was positioned on the vehicle roof). The tasks required negotiating road geometry and other road users. At the end of the session, participants completed the NASA-TLX questionnaire. Results showed that participants completed most tasks faster with the higher viewpoint and reported lower frustration and mental demand. The camera position did not affect collision rates nor the probability of hard braking and steering events. We conclude that a viewpoint from the vehicle roof may improve teleoperation efficiency without compromising driving safety, while also lowering the teleoperators' mental workload.

Cardiac indices of driver fatigue across in-lab and on-road studies.

Driver fatigue is a major contributor to road accidents. Therefore, driver assistance systems (DAS) that would monitor drivers' states may contribute to road safety. Such monitoring can potentially be achieved with input from ECG indices (e.g., heart rate). We reviewed the empirical literature on responses of cardiac measures to driver fatigue and on detecting fatigue with cardiac indices and classification algorithms. We used meta-analytical methods to explore the pooled effect sizes of different cardiac indices of fatigue, their heterogeneity, and the consistency of their responses across studies. Our large pool of studies (N = 39) allowed us to stratify the results across on-road and simulator studies. We found that despite the large heterogeneity of the effect sizes between the studies, many indices had significant pooled effect sizes across the studies, and more frequently across the on-road studies. We also found that most indices showed consistent responses across both on-road and simulator studies. Regarding the detection accuracy, we found that even on-road classification could have been as accurate as 70% with only 2-min of data. However, we could only find two on-road studies that employed fatigue classification algorithms. Overall, our findings are encouraging with respect to the prospect of using cardiac measures for detecting driver fatigue. Yet, to fully explore this possibility, there is a need for additional on-road studies that would employ a similar set of cardiac indices and detection algorithms, a unified definition of fatigue, and additional levels of fatigue than the two fatigue vs alert states.

Relationship between hazard-perception-test scores and proportion of hard-braking events during on-road driving - An investigation using a range of thresholds for hard-braking.

Drivers with higher proportion of hard braking events have greater potential to be involved in an accident. In this study, we tested if hard braking events might be accounted for by drivers' hazard perception (HP) ability. Our investigation was based on an original approach. Usually, researchers define hard braking according to a single deceleration threshold (e.g., g<-0.5). In this study, we chose different thresholds for hard braking (-0.25 to -0.6 g) and for each threshold, we examined the linkage between HP test (HPT) scores and the proportion of hard braking events. We hypothesized that this linkage would be stronger if the threshold that defines hard braking is higher. This is because the stronger the braking events, the higher the likelihood that they resulted from later detection of hazards and the lower the likelihood that they resulted from other causes (e.g., road humps). Thirty-three drivers completed an HPT and used a smartphone app that recorded their vehicle kinematics. We estimated the coefficient of HPT score in a series of binomial regression models on the proportion of hard braking events. In accordance with our hypothesis, we found that the coefficient of HPT score changed as a function of the threshold for hard braking. This finding was based on a significant negative Spearman correlation between the coefficients and the threshold and on linear functions that we derived from two binomial models that allowed the coefficient of HPT to vary according to the threshold. Our findings show that hard braking events are related to HP ability and can inform safety interventions in response to excessive proportion of hard braking events. In addition, they demonstrate that using a range of thresholds for hard braking is a practical tool in the study of hard braking events. From a theoretical perspective, our findings provide strong support to hazard perception theory.

Relationship Between Kinematic and Physiological Indices During Braking Events of Different Intensities.

Objective To study the relationship between physiological indices and kinematic indices during braking events of different intensities. Background Based on mental workload theory, driving and other task demands may generate changes in physiological indices, such as the driver's heart rate and skin conductance. However, no attempts were made to associate changes in physiological indices with changes in vehicle kinematics that result from the driver attempts to meet task demands. Method Twenty-five drivers participated in a field experiment. We manipulated braking demands using roadside signs to communicate the speed (km/h) before braking (50 or 60) and the target speed for braking (30 or to a complete stop). In an additional session, we asked drivers to brake as if they were responding to an impending collision. We analyzed the relationship between the intensities of braking events as measured by deceleration values (g) and changes in heart rate, heart rate variability, and skin conductance. Results All physiological indices were associated with deceleration intensity. Especially salient were the differences in physiological indices between the intensive (|g| > 0.5) and nonintensive braking events. The strongest relationship was between braking intensity and skin conductance. Conclusions Skin conductance, heart rate, and heart rate variability can mirror the mental workload elicited by varying braking intensities. Application Associating vehicle kinematics with physiological indices related to short-term driving events may help improve the performance of driver assistance systems.

Cyclopean, Dominant, and Non-dominant Gaze Tracking for Smooth Pursuit Gaze Interaction.

User-centered design questions in gaze interfaces have been explored in multitude empirical investigations. Interestingly, the question of what eye should be the input device has never been studied. We compared tracking accuracy between the "cyclopean" (i.e., midpoint between eyes) dominant and non-dominant eye. In two experiments, participants performed tracking tasks. In Experiment 1, participants did not use a crosshair. Results showed that mean distance from target was smaller with cyclopean than with dominant or non-dominant eyes. In Experiment 2, participants controlled a crosshair with their cyclopean, dominant and non-dominant eye intermittently and had to align the crosshair with the target. Overall tracking accuracy was highest with cyclopean eye, yet similar between cyclopean and dominant eye in the second half of the experiment. From a theoretical viewpoint, our findings correspond with the cyclopean eye theory of egocentric direction and provide indication for eye dominance, in accordance with the hemispheric laterality approach. From a practical viewpoint, we show that what eye to use as input should be a design consideration in gaze interfaces.

Effects of cues in a binary categorization task on dual-task performance, mental workload, and effort.

Binary cues help operators perform binary categorization tasks, such as monitoring for system failures. They may also allow them to attend to other tasks they concurrently perform. If the time saved by using cues is allocated to other concurrent tasks, users' overall effort may remain unchanged. In 2 experiments, participants performed a simulated quality control task, together with a tracking task. In half the experimental blocks cues were available, and participants could use them in their decisions about the quality of products (intact or faulty). In Experiment 1, the difficulty of tracking was constant, while in Experiment 2, tracking difficulty differed in the 2 halves of the experiment. In both experiments, participants reported on the NASA Task Load Index that cues improved their performance and reduced their frustration. Consequently, their overall score on mental workload (MWL) was lower with cues. They also reported, however, that cues did not reduce their effort. We conclude that cues and other forms of automation may support task performance and reduce overall MWL, but this will not necessarily mean that users will work less hard. Thus, effort and overall MWL should be evaluated separately, if one wants to obtain a full picture of the effects of automation. (PsycINFO Database Record

Effects of cues on target search behavior.

Cues in visual scanning task can improve decision accuracy, and they may also affect task performance strategies. We tested the effects of cues on the performance of binary classifications, on the screen scanning procedure participants employed, and on the reported effort in a simulated quality control task. Participants had to decide whether each item in a 5 × 5 matrix of items was intact or faulty. In half the experimental blocks decisions could only be based on the visual properties of the items. In the other half, participants also saw imperfect binary cues and could use them to classify the items as faulty or intact. We used eye tracking to study scan patterns and fixation durations on items. Decision performance improved with cues, and cues affected the scanning of items, with participants mainly scanning cued items and tending to scan them longer. Participants stated that cues reduced their effort when cues were highly valid. We conclude that strategic choices to focus on suspected areas determined the screen scanning procedure, the amount of effort invested in single decisions, and the accuracy of the decisions. We therefore suggest using likelihood ratio cues to help optimize the scanning procedure.

Mental effort in binary categorization aided by binary cues.

Binary cueing systems assist in many tasks, often alerting people about potential hazards (such as alarms and alerts). We investigate whether cues, besides possibly improving decision accuracy, also affect the effort users invest in tasks and whether the required effort in tasks affects the responses to cues. We developed a novel experimental tool to study binary categorization performance. In two experiments, participants decided whether items on a screen were intact or faulty, based on the configuration of lighter and darker areas in items. Cues were available in half of the experimental blocks, and participants could use them in their decisions. Experimental conditions differed in the effort required to perform the task, manipulated through the contrast between lighter and darker areas (higher contrast vs. lower contrast), and in the validity of cues (medium vs. high validity). In the NASA-TLX, participants reported that with highly valid cues, they invested less effort in the task, whereas with medium validity cues, they invested similar effort as without cues. Responses to the high-validity cues were stronger than responses to the medium-validity cues. The required effort in the task did not affect the strength of responses to cues. We conclude that the invested effort may decrease when cues are available, but users will not rely more strongly on cues in more demanding situations to reduce the invested effort. We therefore recommend integrating cues into work environments, as they reduce users' effort without necessarily leading to overdependence on the cues to reduce invested effort.

User settings of cue thresholds for binary categorization decisions.

The output of binary cuing systems, such as alerts or alarms, depends on the threshold setting-a parameter that is often user-adjustable. However, it is unknown if users are able to adequately adjust thresholds and what information may help them to do so. Two experiments tested threshold settings for a binary classification task based on binary cues. During the task, participants decided whether a product was intact or faulty. Experimental conditions differed in the information participants received: all participants were informed about a product's fault probability and the payoffs associated with decision outcomes; one third also received information regarding conditional probabilities for a fault when the system indicated or did not indicate the existence of one (predictive values); and another third received information about conditional probabilities for the system indicating a fault, in the instance of the existence or lack thereof, of an actual fault (diagnostic values). Threshold settings in all experimental groups were nonoptimal, with settings closest to the optimum with predictive-values information. Results corresponded with a model describing threshold settings as a function of the conditional probabilities for the different outcomes. From a practical perspective, results indicate that predictive-values information best supports decisions about threshold settings. Consequently, for users to adjust thresholds, they should receive information about predictive-values, provided that such values can be computed.