The effects of tunnel radius, turn direction, and zone characteristics on drivers’ visual performance
This study aimed to explore the influence of the tunnel radius, turn direction, and zone characteristics on drivers’ visual performance. The study used a field experiment, in which 30 participants drove real vehicles in different curved tunnels, and measured their fixation duration (FD), fixation frequency (FF), saccade duration (SD), and saccade amplitude (SA) as indicators of visual performance. The results showed that the tunnel radius, turn direction, and zone characteristics had significant effects on all four indicators of visual performance. As the tunnel radius decreases, drivers exhibit longer FD and larger SA, while FF and SD decrease correspondingly. Additionally, the directional aspect of turning significantly influences these eye movement parameters, with drivers demonstrating longer FD, lower FF, shorter SD, and smaller SA during left turns compared to right turns. Irrespective of turning direction, drivers allocate the longest average FD and highest FF in the entrance zone, followed by the middle zone, and the shortest duration in the exit zone under the same tunnel radius condition. Similarly, the mean SD and amplitude are highest in the exit zone, followed by the middle zone, and lowest in the entrance zone, regardless of the turning condition. These findings suggest that drivers adjust their visual behavior according to the dynamic and complex visual stimuli and the varying driving task demands in different scenarios of curved tunnel driving. These findings also imply that drivers face different perceptual and cognitive challenges and preferences when driving in curved tunnels with different radii, turn directions, and zone characteristics, which affect their visual adaptation and preparation processes, as well as their visual integration and differentiation processes. This study has some implications and suggestions for the design and management of curved tunnels, as well as for the education and training of drivers. This study also provides new theoretical and empirical evidence for the visual behavior and cognition of drivers in curved tunnels, and provides practical suggestions for enhancing their visual performance and improving their driving safety and efficiency in curved tunnels.
Training benefits driver behaviour while using automation with an attention monitoring system
Attention, or more generally, driver monitoring systems have been identified as a necessity to address overreliance on driving automation. However, research suggests that monitoring systems may not be sufficient to support safe use of advanced driver assistance systems (ADAS), also evidenced by a recent major recall of Tesla’s monitoring software. The objective of the current study was to investigate whether different training approaches improve driver behaviour while using ADAS with an attention monitoring system. A driving simulator study was conducted with three between-subject groups: no training, limitation-focused training (highlighted situations where ADAS would not work), and responsibility-focused training (highlighted the driver’s role/responsibility while using ADAS). All participants (N = 47) experienced eight events which required the ego-vehicle to slow down to avoid a collision. Anticipatory cues in the environment indicated the potential for the upcoming events. Event type (covered in training vs. not covered) and event criticality (action-necessary vs. action-not-necessary) were within-subject factors. The responsibility-focused group made fewer long glances (≥ 3 s) to a secondary task than the no training and limitation-focused groups when there were no anticipatory cues. Responsibility-focused training and no training were associated with faster takeover time at the events than limitation-focused training. There were additional benefits of responsibility-focused training for events that were covered in training (e.g., higher percent of time looking at the anticipatory cues). Overall, our results suggest that even if attention monitoring systems are implemented, there may be benefits to driver ADAS training. Responsibility-focused training may be preferable to limitation-focused training, especially for situations where minimizing training length is advantageous.
Usability Assessments in User Studies on Human-Machine Interfaces for Conditionally Automated Driving: Effects of the Context of Use
The introduction of conditionally automated driving (CAD) entails a paradigm change in automotive mobility. For the first time, the driver is temporarily released from the responsibility of the driving task. This paradigm change challenges the development of human-machine interfaces (HMIs) facilitating the intended and safe interaction. User studies on the usability of such HMIs are commonly conducted in driving simulators and within one single culture. Identifying the potential effects of this context of use is crucial for the validity of research conducted in the HMI development. Following a review of the relevant literature, five research questions are derived that are addressed in this thesis. A systematic literature review offers insights into common research practices of studies on the usability of HMIs for CAD. Following, a best practice advice is developed. The advice builds the basis for the experimental design for two of the three validation studies conducted in this thesis (Exp_Testing-Environment & Exp_Culture). The first validation study, Exp_Testing-Environment, investigates the effect of the testing environment on usability assessments. An experiment conducted in a static driving simulator is compared to an otherwise identical experiment conducted in an instrumented vehicle on a test track. The findings suggest relative validity but no absolute validity. The study concludes that problems with HMI concepts identified in the driving simulator will likely be more pronounced in test track experiments. Based on the findings, driving simulators are deemed a valid tool. The second validation study, Exp_Culture, investigates the effect of the users’ cultural background on the usability assessment by comparing the usability ratings of U.S.-American participants to German participants. Regarding absolute validity, the database needs to be more conclusive. The findings, however, confirm relative validity. The study concludes that the results of usability assessments may be transferred across cultures of the Western industrialized world. Limitations are expected only regarding the usability facet satisfaction. The third validation study, Survey_Culture, addresses the effect of the users’ cultural background on the subjective importance ratings of usability factors. The comparison of U.S.- American and German ratings shows neither considerable nor systematic cultural effects. In line with Exp_Culture, this study concludes that usability assessments may be conducted within one culture of the Western industrialized world. The findings of the three validation studies are consolidated in a set of preliminary recommendations. The set is discussed and refined in an expert workshop. The final 12 recommendations suggest methods for conducting user studies on the usability of HMIs in the context of CAD. This thesis provides novel empirical findings on experimental methods in user studies on usability assessments, focusing on the validity of usability assessments in varying contexts of use. Based on prevalent literature and an expert workshop, the results are consolidated and refined. Concluding, the thesis contributes to the advancement of valid research methods for conducting usability assessments of HMIs for CAD.
User-Centered Development of Interaction Concepts for a Comfortable and Safe Use of Travel Time in the Context of Fragmented Automated Drives
Automated driving will fundamentally change the way car travel time is utilized. The possibility to engage in a variety of non-driving related activities (NDRAs) is perceived as a major user benefit. However, technical and regulatory restrictions will limit the availability of automated driving functions for the next decades. This will result in fragmented trips consisting of manual, assisted, and automated driving segments. The present thesis seeks to support users of such vehicles in using their drive time as comfortably and safely as possible. Different interaction concepts were developed to support users prior to a drive and during automated and assisted driving. The development followed the user-centered design process. An introductory literature research reveals that users want to be involved in route planning when contrasted with fragmented drives. User requirements for a trip planning tool were derived in a workshop. Based on user needs like travel profiles, prioritization of NDRAs, and an easy-to-interpret visualization of route alternatives, a first prototype was designed, iteratively evaluated, and improved. Finally, a functional smartphone app was developed and evaluated in a usability study. Besides good usability and a high level of intention to use the app, users were able to plan a drive in a short amount of time. Furthermore, the user requirements were highly fulfilled. In addition to the pre-drive phase, the automated driving phase was investigated. During automated driving, NDRAs will be performed on different devices and objects. To prepare users for interruptions caused by transitions to manual or assisted driving, peripherally visible concepts were developed to communicate the remaining time in automated driving in a device-independent and non-interruptive manner. Therefore, a light-emitting diode (LED) stripe was mounted at the bottom of the windshield. In a set of two driving simulator studies, the developed concepts were evaluated positively. However, remaining time estimates will be subject to uncertainty, e.g., due to changing traffic or weather conditions, updated infrastructure information, or unforeseen route changes. Thus, a concept to communicate time budget uncertainties was developed in a small-scale user study. However, the concept using the well-known mobile phone connection icon to convey time budget prediction confidence was rated too complicated in another driving simulator study. Finally, the assisted driving phase was investigated. Users are known to quickly disengage from the monitoring task and rather engage in NDRAs, especially when using a reliable assisted driving function. Thus, a concept to counteract this effect by displaying short motivating pop-up messages was designed in cooperation with usability experts. In a driving simulator study, it was shown to have positive effects on monitoring behavior but did not improve drivers’ reactions to a silent system malfunction. In summary, concepts that can support users in their use of drive time were developed and found to increase comfort and safety in the context of fragmented automated drives. For further implementation, the actual availability and prediction capability of automated driving systems need to be considered.
Visual recognition analysis of optically long tunnels: interaction of dynamic vision and visual perception
To understand the relation between the geometric design of optically long tunnels and visibility of the exit area, in this study oculomotor (eye movement) data are collected from several drivers in Yunnan Province, China, and drivers’ fixation rate and saccade amplitude in the visible zone of the tunnel are measured as key indicators. The driver’s visual recognition is analyzed and key elements in the optimal design of the exit points of optically long tunnels are discussed. The results show that visual recognition is closely associated with the radius of the road curvature: as the radius of curve decreases, the visual focus is gradually attracted to the inner side of the curve, the proportion of small-angle saccade increases, and the dispersion of the saccade amplitude decreases.
Visuomotor coordination with gaze, head and arm movements during table tennis forehand rallies
The purpose of this study was to clarify the temporal coordination between gaze, head, and arm movements during forehand rallies in table tennis. Collegiate male table tennis players (n = 7) conducted forehand rallies at a constant tempo (100, 120, and 150 bpm) using a metronome. In each tempo condition, participants performed 30 strokes (a total of 90 strokes). Gaze, head, and dominant arm (shoulder, elbow, and wrist) movements were recorded with an eye-tracking device equipped with a Gyro sensor and a 3-D motion capture system. The results showed that the effect of head movements relative to gaze movements was significantly higher than that of eye movements in the three tempo conditions. Our results indicate that head movements are closely associated with gaze movements during rallies. Furthermore, cross-correlation coefficients (CCs) between head and arm movements were more than 0.96 (maximum coefficient: 0.99). In addition, head and arm movements were synchronized during rallies. Finally, CCs between gaze and arm movements were more than 0.74 (maximum coefficient: 0.99), indicating that gaze movements are temporally coordinated with arm movements. Taken together, head movements could play important roles not only in gaze tracking but also in the temporal coordination with arm movements during table tennis forehand rallies.
Anticipatory driving in automated vehicles: The effects of driving experience and distraction
Objective: To understand the influence of driving experience and distraction on drivers’ anticipation of upcoming traffic events in automated vehicles. Background: In nonautomated vehicles, experienced drivers spend more time looking at cues that indicate upcoming traffic events compared with novices, and distracted drivers spend less time looking at these cues compared with nondistracted drivers. Further, pre-event actions (i.e., proactive control actions prior to traffic events) are more prevalent among experienced drivers and nondistracted drivers. However, there is a research gap on the combined effects of experience and distraction on driver anticipation in automated vehicles. Methods: A simulator experiment was conducted with 16 experienced and 16 novice drivers in a vehicle equipped with adaptive cruise control and lane-keeping assist systems (resulting in SAE Level 2 driving automation). Half of the participants in each experience group were provided with a self-paced primarily visual-manual secondary task. Results: Drivers with the task spent less time looking at cues and were less likely to perform anticipatory driving behaviors (i.e., pre-event actions or preparation for pre-event actions such as hovering fingers over the automation disengage button). Experienced drivers exhibited more anticipatory driving behaviors, but their attention toward the cues was similar to novices for both task conditions. Conclusion: In line with nonautomated vehicle research, in automated vehicles, secondary task engagement impedes anticipation while driving experience facilitates anticipation. Application: Though Level 2 automation can relieve drivers of manually controlling the vehicle and allow engagement in distractions, visual-manual distraction engagement can impede anticipatory driving and should be restricted.
Comparative Data Analysis of Older Driver’s vs Younger Driver’s Gap Acceptance Behavior at signalized left turns-A driving Simulator Study
Drivers aged 65 and older are particularly prone to motor vehicle crashes, with approximately 20% of traffic fatalities occurring at intersections [11]. Intersections appear to be hazardous for drivers in this age group due to cognitive, perceptual, and psychomotor challenges. Older drivers find it particularly difficult to safely navigate left turns at signalized permissive intersections, having problems adequately detecting, perceiving, and accurately judging the safety of gaps. The increase in the number of elderly drivers has been paralleled by an increase in road-related accidents due to age-related fragility. By 2030, more than 21% of the adult population is projected to be over 65 years old [1]. However, previous studies have not adequately considered the combined effects of the randomized gap, queue length, traffic volume, pedestrians, and physiological factors on driving. The current study aims to address the gap in the literature by explicitly examining older and younger drivers’ gap acceptance behaviors during permissive left turns at four-way intersections. The main objective of this thesis is to study, identify and analyze the effect of Gap Acceptance Behavior on age, traffic volume, queue length, and physiological factors such as heart rate variability (HRV), electrodermal activity (EDA), and motion sickness among older and younger drivers. The data was collected from a driving simulator study comprising 40 participants aged between 20-30 for younger and 65 years for older. The collected data was used for comparative analysis, with the Gap Accepted by the drivers calculated from the video data. The gap is calculated as the distance between the left turning vehicle and the oncoming traffic. All recruited drivers were healthy. Each participant navigated twelve scenarios, six with lower traffic conditions and six with higher traffic conditions. Each lower and higher traffic scenario varied in queue length, with the number of cars in front of the ego vehicle varying from 0, 1, and 2. All varying queue lengths also had one with a pedestrian and another without. The physiological data collected through the Empatica4 wristband was also considered to study the gap acceptance behavior. Another parameter, motion sickness susceptibility score (MSSQ), was obtained from a questionnaire the participants completed after the experiment. Of these factors, queue length, traffic volume, and pedestrians play a significant role in studying gap acceptance. There is a significant difference in accepting and rejecting the gap between young and older drivers. Older drivers’ decision is affected more by factors, such as traffic volume, age, queue length, HRV, EDA, MSSQ score and the presence of pedestrians. This study showed that older drivers exhibited longer gap acceptance times than their younger counterparts while turning left across traffic at permissive intersections. Researchers may use the findings to better understand gap acceptance behaviors, while policymakers may utilize the results to design mobility guidelines.
