Use of Pupil Area and Fixation Maps to Evaluate Visual Behavior of Drivers inside Tunnels at Different Luminance Levels—A Pilot Study
This study reports the results of a pilot study on spatiotemporal characteristics of drivers’ visual behavior while driving in three different luminance levels in a tunnel. The study was carried out in a relatively long tunnel during the daytime. Six experienced drivers were recruited to participate in the driving experiment. Experimental data of pupil area and fixation point position (at the tunnel’s interior zone: 1566 m long) were collected by non-intrusive eye-tracking equipment at three luminance levels (2 cd/m2, 2.5 cd/m2, and 3 cd/m2). Fixation maps (color-coded maps presenting distributed data) were created based on fixation point position data to quantify changes in visual behavior. The results demonstrated that luminance levels had a significant effect on pupil areas and fixation zones. Fixation area and average pupil area had a significant negative correlation with luminance levels during the daytime. In addition, drivers concentrated more on the front road pavement, the top wall surface, and the cars’ control wheels. The results revealed that the pupil area had a linear relationship with the luminance level. The limitations of this research are pointed out and the future research directions are also prospected.
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Validity of primary driving tasks in head-mounted display-based driving simulators
The development of new car interior concepts requires tools, particularly in development phases before concept milestones, which enable subjective experiences and evaluations in static and driving situations. On the one hand, variant comparisons are necessary; on the other hand, the level of immersion should be high enough that participants can behave as they would in real cars. Virtual reality technologies and especially head-mounted displays are generally very suitable for such evaluations with the exception being in state-of-the-art driving simulators. Therefore, a validation study was undertaken in which primary driving tasks in two HMD-based simulators were compared with test runs in a real car. The difference between the simulators was only the state of the motion base (enabled vs. disabled). In both simulators and the test runs in the real car, four identical scenarios (straight, curves, overtaking and junction) were carried out. Since the focus is primarily on subjective ratings and gaze behaviour when evaluating new car interior concepts, in this study gaze behaviour was also priority. In addition, driving dynamics parameters were measured. The results reveal that the participants show more valid behaviour in the dynamic system than in the static simulator condition.
Visual enhancements for the driver’s information search on automotive head-up display
In the past, in-vehicle head-up displays (HUDs) were used to display simple information including driving speed and the distance between cars. However, recent HUDs now display complex information such as advanced driver assistance information. This study aims to identify the effects of visual enhancements for HUDs on the driver’s performance and workload. Twenty participants conducted the tracking tasks for information search while driving in an automotive simulator environment. The participants experienced three levels of visual enhancements (none, shaded reference bar, translucent reference bar) for each task difficulty (low, medium, high). The results showed that visual enhancements and task difficulties had a significant effect on the tracking errors and subjective workloads. These findings verify that the translucent reference bar significantly improved the tracking performance. Furthermore, the visual enhancement cues on the HUDs play an important role in visual search. This research provides practical guidelines to ensure road safety through minimizing cognitive workload on drivers. Therefore, the results will encourage interface designers to consider the visual enhancement for HUDs from a user-centered perspective.
Analysis of Visual Search Characteristics Based on Drivers’ Hazard Perception
In order to study the driver’s visual search characteristics, eye movement analysis is used to measure drivers’ hazard perception in different scenarios. The mechanical division method is used to divide the field of driver’s vision into five areas, considered potential danger miss rate as the indicator of the driver’s hazard perception evaluation to analysis drivers’ visual search characteristics, and the saccade or fixation in the driver’s hazard perception process. Results show that drivers mainly obtain traffic information through near area in front of road, distant area in front of road, and potentially dangerous source areas. Drivers with high hazard perception have a wider visual search range, which can identify potential dangers more quickly and accurately. Moreover, drivers with high hazard perception tend to pay more visual attention to near road and the danger area, the visual search scope is more comprehensive, and the visual search strategy is more effective.
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Drivers’ visual load at different time periods in entrance and exit zones of extra-long tunnel
Objective: As the number of tunnels and traffic accidents increase, it is necessary to study the drivers’ visual characteristic in the tunnels. Considering that freeway tunnels have limited space and narrow sight zone, drivers usually have a short visual blind zone and visual shock when entering and exiting the tunnels. This study aims to investigate the characteristics of drivers’ visual load in the entrance and exit zones of extra-long tunnels, and to provide a theoretical basis for the traffic safety prevention and control measures of the engineering design. Methods: 20 drivers were enrolled to conduct real vehicle tests in the Guizhou Sifangdong Tunnel at different time periods (daytime, twilight, and nighttime). The drivers’ pupil area was collected by an eye tracker. The maximum transient vibration value (MTVV) of the pupil area was selected as the index of visual load. In addition, the changing characteristics of visual load in the entrance and exit zones were examined. Using ANOVA, the significant difference of visual load in different zones and at different time periods were performed. Accordingly, the overall drivers’ visual load in the entrance and the exit zones were compared. Exponential function models of the MTVV value and the speed of pupil area change were constructed, where the pattern of mutual influence was examined. Results: The changing pattern of the drivers’ visual load at different time periods in the entrance and exit zones were markedly different. The comparison of the overall visual load was as follows: exit zones at nighttime > entrance zones at nighttime > entrance zones at twilight > exit zones at twilight ≈ entrance zones at daytime ≈ exit zones at daytime. Moreover, the MTVV value positively correlated with the speed of the pupil area change. Finally, this study proposes an evaluation standard of visual comfort based on the speed of the pupil area change. Conclusion: This study highlights the driving risk in extra-long tunnel. These findings could provide a basis for studying the setting method of visual guidance facilities in entrance and exit zones of extra-long tunnel. Also, this study could provide a theoretical basis for the evaluation of drivers’ visual load in the tunnel.
EEG-based assessment in novice and experienced drivers’ braking behaviour during simulated driving
The driver is an essential factor in the traffic system, and inexperienced drivers are special high-risk groups. We used electroencephalography (EEG) and reaction time to quantify the differences between experienced and novice drivers' risk perception and braking behaviour in a driving simulator. Twenty-seven participants were asked to drive through a 12-km dynamic scenario with EEG signals recorded simultaneously. There are mainly four frequency bands for human EEG activity: alpha, beta, theta, and delta. The power spectral density (PSD) of beta activity was analysed because it dominated when drivers braked in an emergency. The results indicate that the indicators of β activity and reaction time discriminated between the novice and experienced drivers. The reaction time of drivers was related to the increment of the β activity, indicating that the driver's risk perception stage will affect their risk reaction. The study provides us with the operating performance and internal physiological activities of drivers in the braking process.
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Evaluation of ambient light displays for requests to intervene and minimal risk maneuvers in highly automated urban driving
Driver take-overs at system limits and the corresponding requests to intervene are not obligatory in highly automated driving. Therefore, minimal risk maneuvers may occur. In order to clearly communicate the automation status and the driver's task at such system limits, ambient light displays seem to have a high potential. Therefore, two ambient light displays were investigated in a driving simulation experiment, mounted either at the bottom of the windshield or on the steering wheel. Forty participants experienced two request to intervene scenarios, and two minimal risk maneuver scenarios during a highly automated drive. In general, both ambient light displays seem to ensure correct driver's reactions and safety, and lead to positive subjective ratings. Results revealed no significant differences between the two ambient light display positions regarding the take-over behavior, gaze behavior and subjective rating, except in terms of the perceived brightness.
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Expert drivers’ prospective thinking-aloud to enhance automated driving technologies–Investigating uncertainty and anticipation in traffic
Current automated driving technology cannot cope in numerous conditions that are basic daily driving situations for human drivers. Previous studies show that profound understanding of human drivers’ capability to interpret and anticipate traffic situations is required in order to provide similar capacities for automated driving technologies. There is currently not enough a priori understanding of these anticipatory capacities for safe driving applicable to any given driving situation. To enable the development of safer, more economical, and more comfortable automated driving experience, expert drivers’ anticipations and related uncertainties were studied on public roads. First, driving instructors’ expertise in anticipating traffic situations was validated with a hazard prediction test. Then, selected driving instructors drove in real traffic while thinking aloud anticipations of unfolding events. The results indicate sources of uncertainty and related adaptive and social behaviors in specific traffic situations and environments. In addition, the applicability of these anticipatory capabilities to current automated driving technology is discussed. The presented method and results can be utilized to enhance automated driving technologies by indicating their potential limitations and may enable improved situation awareness for automated vehicles. Furthermore, the produced data can be utilized for recognizing such upcoming situations, in which the human should take over the vehicle, to enable timely take-over requests.
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Gender aspects of trust in and use of advanced driver assistance systems/submitted by Gina Nathalie Schnücker
Increasing automation in vehicles promises an equal increase in driving safety and comfort. Current research aims to identify factors that influence if and how in-vehicle automation is adopted by the human operator. Trust in automation was identified to be one of those factors. Still, there is a need to understand the relationship between system-trust and actual reliance behavior. Therefore, the first aim of this thesis was to investigate the relationship between trust in Advanced Driver Assistance Systems and actual reliance behavior. The second aim was to address the inconsistencies in previous research regarding gender differences in automation trust by introducing the concept of gender roles. The concept of gender roles addresses stereotypical behavior associated with masculinity and femininity rather than biological sex and has already been identified to explain variance in addition and beyond biological sex in manual driving, risk-taking, and technology adoption. Qualitative, quantitative, and psychophysiological data were integrated in an experiment with 100 participants (49 females) in a 25-minute field-drive. We assessed attitudes and behavior in interaction with a Lane Keeping Assist (LA), that supports the driver to keep the vehicle within the lane and the Adaptive Cruise Control (ACC) that maintains a set speed and keeps a set distance to preceding vehicles. The results show that trust after the automated drive was positively related to the use of the LA and the simultaneous use of LA and ACC. It also showed that there were no sex differences in trust and reliance behavior. In contrast, masculinity was positively related to trust before the automated drive, while femininity was positively related to trust after the drive. These findings have implications for trust measurement and the promotion of a safe adoption of in-vehicle automation.
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Human Factors Studies on Automotive Head-Up Display Design
Human Factors Studies on Automotive Head-Up Display Design Juhee Park Department of Industrial Engineering The Graduate School Seoul National University Head-up display (HUD) systems were introduced into the automobile industry as a means for improving driving safety. They superimpose safety-critical information on top of the driver’s forward field of view and thereby help drivers keep their eyes forward while driving. Since the first introduction about three decades ago, automotive HUDs have been available in various commercial vehicles. Despite the long history and potential benefits of automotive HUDs, however, the design of useful automotive HUDs remains a challenging problem. In an effort to contribute to the design of useful automotive HUDs, this doctoral dissertation research conducted four studies. In Study 1, the functional requirements of automotive HUDs were investigated by reviewing the major automakers' automotive HUD products, academic research studies that proposed various automotive HUD functions, and previous research studies that surveyed drivers’ HUD information needs. The review results indicated that: 1) the existing commercial HUDs perform largely the same functions as the conventional in-vehicle displays, 2) past research studies proposed various HUD functions for improving driver situation awareness and driving safety, 3) autonomous driving and other new technologies are giving rise to new HUD information, and 4) little research is currently available on HUD users’ perceived information needs. Based on the review results, this study provides insights into the functional requirements of automotive HUDs and also suggests some future research directions for automotive HUD design. In Study 2, the interface design of automotive HUDs for communicating safety-related information was examined by reviewing the existing commercial HUDs and display concepts proposed by academic research studies. Each display was analyzed in terms of its functions, behaviors and structure. Also, related human factors display design principles, and, empirical findings on the effects of interface design decisions were reviewed when information was available. The results indicated that: 1) information characteristics suitable for the contact-analog and unregistered display formats, respectively, are still largely unknown, 2) new types of displays could be developed by combining or mixing existing displays or display elements at both the information and interface element levels, and 3) the human factors display principles need to be used properly according to the situation and only to the extent that the resulting display respects the limitations of the human information processing, and achieving balance among the principles is important to an effective design. On the basis of the review results, this review suggests design possibilities and future research directions on the interface design of safety-related automotive HUD systems. In Study 3, automotive HUD-based take-over request (TOR) displays were developed and evaluated in terms of drivers’ take-over performance and visual scanning behavior in a highly automated driving situation. Four different types of TOR displays were comparatively evaluated through a driving simulator study - they were: Baseline (an auditory beeping alert), Mini-map, Arrow, and Mini-map-and-Arrow. Baseline simply alerts an imminent take-over, and was always included when the other three displays were provided. Mini-map provides situational information. Arrow presents the action direction information for the take-over. Mini-map-and-Arrow provides the action direction together with the relevant situational information. This study also investigated the relationship between driver’s initial trust in the TOR displays and take-over and visual scanning behavior. The results indicated that providing a combination of machine-made decision and situational information, such as Mini-map-and-Arrow, yielded the best results overall in the take-over scenario. Also, drivers’ initial trust in the TOR displays was found to have significant associations with the take-over and visual behavior of drivers. The higher trust group primarily relied on the proposed TOR displays, while the lower trust group tended to more check the situational information through the traditional displays, such as side-view or rear-view mirrors. In Study 4, the effect of interactive HUD imagery location on driving and secondary task performance, driver distraction, preference, and workload associated with use of scrolling list while driving were investigated. A total of nine HUD imagery locations of full-windshield were examined through a driving simulator study. The results indicated the HUD imagery location affected all the dependent measures, that is, driving and task performance, drivers’ visual distraction, preference and workload. Considering both objective and subjective evaluations, interactive HUDs should be placed near the driver's line of sight, especially near the left-bottom on the windshield.
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