Toward overtrust-free advanced driver assistance systems

Avoiding human overtrust in machines is a vital issue to establish a socially acceptable advanced driver assistance system (ADAS). However, research has not clarified the effective way of designing an ADAS to prevent driver overtrust in the system. It is necessary to develop a theoretical framework that is useful to understand how a human trust becomes excessive. This paper proposes a trust model by which overtrust can be clearly defined. It is shown that at least three types of overtrust are distinguished on the basis of the model. As an example, this paper discusses human overtrust in an adaptive cruise control (ACC) system. By conducting an experiment on a medium-fidelity driving simulator, we observed two types of overtrust among the three. The first one is that some drivers relied on the ACC system beyond its limit of decelerating capability. The second one is that a driver relied on the ACC systems by expecting that it could decelerate against a stopped vehicle. It is estimated through data analysis how those kinds of overtrust emerged. Furthermore, the possible ways for prevention of human overtrust in ADAS are discussed.     

Making adaptive cruise control (ACC) limits visible

Previous studies have shown adaptive cruise control (ACC) can compromise driving safety when drivers do not understand how the ACC functions, suggesting that drivers need to be informed about the capabilities of this technology. This study applies ecological interface design (EID) to create a visual representation of ACC behavior, which is intended to promote appropriate reliance and support effective transitions between manual and ACC control. The EID display reveals the behavior of ACC in terms of time headway (THW), time to collision (TTC), and range rate. This graphical representation uses emergent features that signal the state of the ACC. Two failure modes—exceedance of braking algorithm limits and sensor failures—were introduced in the driving contexts of traffic and rain, respectively. A medium-fidelity driving simulator was used to evaluate the effect of automation (manual, ACC control), and display (EID, no display) on ACC reliance, brake response, and driver intervention strategies. Drivers in traffic conditions relied more appropriately on ACC when the EID display was present than when it was not, proactively disengaging the ACC. The EID display promoted faster and more consistent braking responses when braking algorithm limits were exceeded, resulting in safe following distances and no collisions. In manual control, the EID display aided THW maintenance in both rain and traffic conditions, reducing the demands of driving and promoting more consistent and less variable car-following performance. These results suggest that providing drivers with continuous information about the state of the automation is a promising alternative to the more common approach of providing imminent crash warnings when it fails. Informing drivers may be more effective than warning drivers.     

Driver behaviour with adaptive cruise control

This paper reports on the evaluation of adaptive cruise control (ACC) from a psychological perspective. It was anticipated that ACC would have an effect upon the psychology of driving, i.e. make the driver feel like they have less control, reduce the level of trust in the vehicle, make drivers less situationally aware, but workload might be reduced and driving might be less stressful. Drivers were asked to drive in a driving simulator under manual and ACC conditions. Analysis of variance techniques were used to determine the effects of workload (i.e. amount of traffic) and feedback (i.e. degree of information from the ACC system) on the psychological variables measured (i.e. locus of control, trust, workload, stress, mental models and situation awareness). The results showed that: locus of control and trust were unaffected by ACC, whereas situation awareness, workload and stress were reduced by ACC. Ways of improving situation awareness could include cues to help the driver predict vehicle trajectory and identify conflicts.     

Driver behaviour with adaptive cruise control

This paper reports on the evaluation of adaptive cruise control (ACC) from a psychological perspective. It was anticipated that ACC would have an effect upon the psychology of driving, i.e. make the driver feel like they have less control, reduce the level of trust in the vehicle, make drivers less situationally aware, but workload might be reduced and driving might be less stressful. Drivers were asked to drive in a driving simulator under manual and ACC conditions. Analysis of variance techniques were used to determine the effects of workload (i.e. amount of traffic) and feedback (i.e. degree of information from the ACC system) on the psychological variables measured (i.e. locus of control, trust, workload, stress, mental models and situation awareness). The results showed that: locus of control and trust were unaffected by ACC, whereas situation awareness, workload and stress were reduced by ACC. Ways of improving situation awareness could include cues to help the driver predict vehicle trajectory and identify conflicts.     

Trust and the use of adaptive cruise control: a study of a cut-in situation

This paper analyses driver trust and performance when using adaptive cruise control (ACC) in a situation involving a truck cutting into the lane in front of the ACC-equipped vehicle. The study was carried out using a mini driving simulator and a simulated ACC whose reference speed and time headway (THW) were preset to 130 km/h and 1.5 s, respectively. Questionnaires were used to analyse driver trust. Two kinds of drivers emerge from the analysis of driver behaviour during the cut-in situation: drivers who reclaimed control from the ACC before the device began to regulate the THW with regard to the truck, and drivers who braked after the device had begun its regulation. The latter demonstrated a higher level of trust in the ACC device itself while the former had a higher level of trust in the cooperation with the device. These findings are discussed in terms of over-reliance and well-calibrated trust.     

Driver sensitivity to brake pulse duration and magnitude

Adaptive cruise control (ACC) requires that the driver intervene in situations that exceed the capability of ACC. A brake pulse might provide a particularly compatible means of alerting the driver to situations in which the acceleration authority of the ACC has been exceeded. This study examined the sensitivity of the driver to brake pulses of five different amplitudes (0.01-0.025 g) and five different durations (50-800 ms). Drivers were sensitive to accelerations as low as 0.015 g. Pulse duration interacted with pulse amplitude, such that moderate duration pulses were more detectable than long and short duration pulses at intermediate levels of pulse amplitude. A power function with an exponent of 1.0 accounted for 99% of the variance in drivers' sensitivity to pulse amplitude; however, a power function with an exponent of 0.23 accounted for only 70% of the variance in drivers' sensitivity to pulse duration. These results can help designers create ACC algorithms and develop brake pulse warnings.     

Driver sensitivity to brake pulse duration and magnitude

Adaptive cruise control (ACC) requires that the driver intervene in situations that exceed the capability of ACC. A brake pulse might provide a particularly compatible means of alerting the driver to situations in which the acceleration authority of the ACC has been exceeded. This study examined the sensitivity of the driver to brake pulses of five different amplitudes (0.01–0.025 g) and five different durations (50–800 ms). Drivers were sensitive to accelerations as low as 0.015 g. Pulse duration interacted with pulse amplitude, such that moderate duration pulses were more detectable than long and short duration pulses at intermediate levels of pulse amplitude. A power function with an exponent of 1.0 accounted for 99% of the variance in drivers' sensitivity to pulse amplitude; however, a power function with an exponent of 0.23 accounted for only 70% of the variance in drivers' sensitivity to pulse duration. These results can help designers create ACC algorithms and develop brake pulse warnings.     

The role of intervening variables in driver–ACC cooperation

This paper analyzes the behavior of drivers using Adaptive Cruise Control (ACC) within the theoretical framework of Human–Machine Cooperation. The study was carried out on a driving simulator. Driving task performance data and responses to a trust questionnaire were analyzed in order to examine the relationship between driver reliance on ACC and such intervening variables as trust, perceived workload and perceived risk. The participants were divided a posteriori into two groups according to their use of the ACC device during the experimental run. The results show that high-use drivers seemed to cooperate more with ACC than low-use drivers, who tended to perceive more risk and a higher workload. These findings are discussed in the light of Riley's theory of operator reliance on automation.     

Design,tuning, and evaluation of a full-range adaptive cruise control system with collision avoidance

This paper describes the design, tuning, and evaluation of a full-range adaptive cruise control (ACC) system with collision avoidance (CA). The control scheme is designed to improve drivers’ comfort during normal, safe-driving situations and to completely avoid rear-end collision in vehicle-following situations. Driving situations are divided into safe, warning, and dangerous modes. Three different control strategies have been proposed, depending on the driving situation. The driving situations are determined using a non-dimensional warning index and the time-to-collision (TTC). The control parameters of the proposed ACC/CA system are tuned by a confusion-matrix method using manual-driving data in no-crashing driving situations. The vehicle-following characteristics of the subject vehicle were compared to real-world, manual-driving data. Finally, the ACC/CA system was also implemented in a real vehicle and tested in both safe-traffic and severe-braking situations. It is shown that the proposed control strategy can provide natural following performance that is similar to human manual-driving in both high-speed driving and low-speed stop-and-go situations. Furthermore, it can prevent the vehicle-to-vehicle distance from dropping to an unsafe level in a variety of driving conditions.     

Effectiveness and driver acceptance of a semi-autonomous forward obstacle collision avoidance system

This paper proposes a semi-autonomous collision avoidance system for the prevention of collisions between vehicles and pedestrians and objects on a road. The system is designed to be compatible with the human-centered automation principle, i.e., the decision to perform a maneuver to avoid a collision is made by the driver. However, the system is partly autonomous in that it turns the steering wheel independently when the driver only applies the brake, indicating his or her intent to avoid the obstacle. With a medium-fidelity driving simulator, we conducted an experiment to investigate the effectiveness of this system for improving safety in emergency situations, as well as its acceptance by drivers. The results indicate that the system effectively improves safety in emergency situations, and the semi-autonomous characteristic of the system was found to be acceptable to drivers.     

Can we make operating systems reliable and secure?

Microkernels long discarded as unacceptable because of their lower performance compared with monolithic kernels might be making a comeback in operating systems due to their potentially higher reliability, which many researchers now regard as more important than performance. Each of the four different attempts to improve operating system reliability focuses on preventing buggy device drivers from crashing the system. In the Nooks approach, each driver is individually hand wrapped in a software jacket to carefully control its interactions with the rest of the operating system, but it leaves all the drivers in the kernel. The paravirtual machine approach takes this one step further and moves the drivers to one or more machines distinct from the main one, taking away even more power from the drivers. Both of these approaches are intended to improve the reliability of existing (legacy) operating systems. In contrast, two other approaches replace legacy operating systems with more reliable and secure ones. The multiserver approach runs each driver and operating system component in a separate user process and allows them to communicate using the microkernel's IPC mechanism. Finally, Singularity, the most radical approach, uses a type-safe language, a single address space, and formal contracts to carefully limit what each module can do.     

User-centred design evaluation of symbols for adaptive cruise control (ACC) and lane-keeping assistance (LKA)

Advanced driving assistance systems (ADAS) are now numerous, each relieving drivers of their responsibility for the control of different aspects of the driving task. Notably, adaptive cruise control (ACC) for longitudinal control, or lane departure prevention (LDP) and lane centring control (LCC) for lateral control, two variations of the lane-keeping assistance (LKA) system. Drivers must familiarise themselves with various symbols to correctly identify and activate the system they wish to be using and the existing standard graphical symbols for ACC and LKA are often replaced by manufacturers in favour of their own symbols. With a user-centred approach in mind, we previously conducted a focus group where drivers were invited to design their own symbols and discuss those symbols currently in-use. In the present research, we administered an online survey and analysed the responses from 328 drivers regarding different levels of knowledge about ADAS, to evaluate the usability of a selection of these symbols. Our results indicate that the standard ACC symbol would not be the most suitable of the four symbols tested, whereas, the standard LKA/LDP symbol was greatly confused with any of the four LCC symbols we tested, especially if hands were present on the symbol. Finally, drivers without prior knowledge of ADAS had more difficulties interpreting those symbols in general. Considerations for the development and evaluation of graphical symbols are discussed.

     

Decision-Making in Driver-Automation Shared Control: A Review and Perspectives

Shared control schemes allow a human driver to work with an automated driving agent in driver-vehicle systems while retaining the driver’s abilities to control. The human driver, as an essential agent in the driver-vehicle shared control systems, should be precisely modeled regarding their cognitive processes, control strategies, and decision-making processes. The interactive strategy design between drivers and automated driving agents brings an excellent challenge for human-centric driver assistance systems due to the inherent characteristics of humans. Many open-ended questions arise, such as what proper role of human drivers should act in a shared control scheme? How to make an intelligent decision capable of balancing the benefits of agents in shared control systems? Due to the advent of these attentions and questions, it is desirable to present a survey on the decision making between human drivers and highly automated vehicles, to understand their architectures, human driver modeling, and interaction strategies under the driver-vehicle shared schemes. Finally, we give a further discussion on the key future challenges and opportunities. They are likely to shape new potential research directions.      

On-line driver workload estimation. Effects of road situation and age on secondary task measures

In order to develop a driver-car interface that adapts the presentation of messages generated by in-vehicle information systems to driver workload, two experiments investigated potential determinants of driver visual and mental workload as indicated by performance on two secondary tasks. Experiment 1 suggested that road situation is a major determinant of visual and mental workload of the driver and that the processing resources of older drivers are somewhat more limited than those of younger and middle-aged drivers. Familiarity with the area of driving (when guided) and time of day (associated with traffic density) showed no secondary task effects. Experiment 2 showed that the categorization of road situations, proposed in Experiment 1, could underlie adaptation of visually loading messages to the workload incurred by driving. This was not found with respect to mentally loading messages.     

On-line driver workload estimation. Effects of road situation and age on secondary task measures

In order to develop a driver-car interface that adapts the presentation of messages generated by in-vehicle information systems to driver workload, two experiments investigated potential determinants of driver visual and mental workload as indicated by performance on two secondary tasks. Experiment 1 suggested that road situation is a major determinant of visual and mental workload of the driver and that the processing resources of older drivers are somewhat more limited than those of younger and middle-aged drivers. Familiarity with the area of driving (when guided) and time of day (associated with traffic density) showed no secondary task effects. Experiment 2 showed that the categorization of road situations, proposed in Experiment 1, could underlie adaptation of visually loading messages to the workload incurred by driving. This was not found with respect to mentally loading messages.     

Analysis and modeling of human driving behaviors using adaptive cruise control

We describe a driver model based on the feedback-error learning scheme using neural network (NN) for adaptive cruise control (ACC) use in driving and show the applicability of the feedback-error learning scheme as a behavior model of adaptability of human. The focus of the study is on the adaptation process of driving behaviors using ACC. The driver model for computer simulations was implemented by using a NN. The developed simulation model is used for predicting control performance of skilled driver using ACC. In the experiments, we used a fixed-base driving simulator (DS) installed ACC system for collecting driver’s data. Headway time when lane changing in a row and lateral deviation from road center were investigated as driver behavior characteristics during ACC use and manual driving, respectively. The simulation results of the lateral deviation were compared with the experimental results and showed that control performance with ACC use would be better than that of manual driving. Furthermore, it was found that human error occurred during ACC use in the DS experiments and provided an explanation of the cause in terms of Neisser’s perceptual cycle model.     

Influences of braking system faults on vehicle dynamics

From a safety point of view, the braking system is, besides the driver, one of the key subsystems in a car. The driver, as an adaptive control system, might not notice small faults in the hydraulic part of the braking system and sooner or later critical braking situations, e.g. due to a brake-circuit failure, may occur. Most drivers are not capable of dealing with such critical situations. Therefore, this paper investigates the influence of faults in the braking system on the dynamic vehicle behavior and the steering inputs of the driver required to keep the vehicle on the desired course.     

Warn me now or inform me later: Drivers' acceptance of real-time and post-drive distraction mitigation systems

Vehicle crashes caused by driver distraction are of increasing concern. One approach to reduce the number of these crashes mitigates distraction by giving drivers feedback regarding their performance. For these mitigation systems to be effective, drivers must trust and accept them. The objective of this study was to evaluate real-time and post-drive mitigation systems designed to reduce driver distraction. The real-time mitigation system used visual and auditory warnings to alert the driver to distracting behavior. The post-drive mitigation system coached drivers on their performance and encouraged social conformism by comparing their performance to peers. A driving study with 36 participants between the ages of 25 and 50 years old (M=34) was conducted using a high-fidelity driving simulator. An extended Technology Acceptance Model captured drivers' acceptance of mitigation systems using four constructs: perceived ease of use, perceived usefulness, unobtrusiveness, and behavioral intention to use. Perceived ease of use was found to be the primary determinant and perceived usefulness the secondary determinant of behavioral intention to use, while the effect of unobtrusiveness on intention to use was fully mediated by perceived ease of use and perceived usefulness. The real-time system was more obtrusive and less easy to use than the post-drive system. Although this study included a relatively narrow age range (25 to 50 years old), older drivers found both systems more useful. These results suggest that informing drivers with detailed information of their driving performance after driving is more acceptable than warning drivers with auditory and visual alerts while driving.     

Effects of an in-vehicle collision avoidance warning system on short- and long-term driving performance

Many new in-vehicle systems focus on accident prevention by facilitating the driving task. One such driving aid is an in-vehicle collision avoidance warning system (IVCAWS), used to alert the driver to an impending collision. Our study evaluated the effects of an imperfect IVCAWS both on driver headway maintenance and on driver behavior in response to warning system errors. Our results showed that drivers tend to overestimate their headway and consequently drive with short and potentially dangerous headways, and that IVCAWSs are a useful tool for educating drivers to estimate headway more accurately. Moreover, our study showed that after a relatively short exposure to the system, drivers were able to maintain longer and safer headways for at least six months. The practical implications of these results are that the use of an IVCAWS should be considered for inclusion in driver education and training programs.