Trust in automated vehicles: constructs, psychological processes, and assessment.

There is a growing body of research on trust in driving automation systems. In this paper, we seek to clarify the way trust is conceptualized, calibrated and measured taking into account issues related to specific levels of driving automation. We find that: (1) experience plays a vital role in trust calibration; (2) experience should be measured not just in terms of distance traveled, but in terms of the range of situations encountered; (3) system malfunctions and recovery from such malfunctions is a fundamental part of this experience. We summarize our findings in a framework describing the dynamics of trust calibration. We observe that methods used to quantify trust often lack objectivity, reliability, and validity, and propose a set of recommendations for researchers seeking to select suitable trust measures for their studies. In conclusion, we argue that the safe deployment of current and future automated vehicles depends on drivers developing appropriate levels of trust. Given the potentially severe consequences of miscalibrated trust, it is essential that drivers incorporate the possibility of new and unexpected driving situations in their mental models of system capabilities. It is vitally important that we develop methods that contribute to this goal.

External Human-Machine Interfaces for Automated Vehicles in Shared Spaces: A Review of the Human-Computer Interaction Literature.

Given the rise of automated vehicles from an engineering and technical perspective, there has been increased research interest concerning the Human and Computer Interactions (HCI) between vulnerable road users (VRUs, such as cyclists and pedestrians) and automated vehicles. As with all HCI challenges, clear communication and a common understanding-in this application of shared road usage-is critical in order to reduce conflicts and crashes between the VRUs and automated vehicles. In an effort to solve this communication challenge, various external human-machine interface (eHMI) solutions have been developed and tested across the world. This paper presents a timely critical review of the literature on the communication between automated vehicles and VRUs in shared spaces. Recent developments will be explored and studies analyzing their effectiveness will be presented, including the innovative use of Virtual Reality (VR) for user assessments. This paper provides insight into several gaps in the eHMI literature and directions for future research, including the need to further research eHMI effects on cyclists, investigate the negative effects of eHMIs, and address the technical challenges of eHMI implementation. Furthermore, it has been underlined that there is a lack of research into the use of eHMIs in shared spaces, where the communication and interaction needs differ from conventional roads.

Under pressure: Effect of a ransomware and a screen failure on trust and driving performance in an automated car simulation.

One major challenge for automated cars is to not only be safe, but also secure. Indeed, connected vehicles are vulnerable to cyberattacks, which may jeopardize individuals' trust in these vehicles and their safety. In a driving simulator experiment, 38 participants were exposed to two screen failures: silent (i.e., no turn signals on the in-vehicle screen and instrument cluster) and explicit (i.e., ransomware attack), both while performing a non-driving related task (NDRT) in a conditionally automated vehicle. Results showed that objective trust decreased after experiencing the failures. Drivers took over control of the vehicle and stopped their NDRT more often after the explicit failure than after the silent failure. Lateral control of the vehicle was compromised when taking over control after both failures compared to automated driving performance. However, longitudinal control proved to be smoother in terms of speed homogeneity compared to automated driving performance. These findings suggest that connectivity failures negatively affect trust in automation and manual driving performance after taking over control. This research posits the question of the importance of connectivity in the realm of trust in automation. Finally, we argue that engagement in a NDRT while riding in automated mode is an indicator of trust in the system and could be used as a surrogate measure for trust.

Urban air mobility infrastructure design: Using virtual reality to capture user experience within the world's first urban airport.

Human factors research can play an important role in the successful design of infrastructure to support future mobility. Through engaging users and stakeholders early in the design process we can gain insights before the physical environments are built. This paper presents data from a truly novel application of Virtual Reality (VR), where user experience and wayfinding were evaluated within an emerging future transport infrastructure to support urban air mobility (UAM) - the urban airport (aka vertiports). Urban airports are located in city centres where drones or 'flying cars' would land and take off from. Previous quantitative studies have investigated passenger experience in traditional airports using field observation and surveys, but this paper is the first to present qualitative research on user experience in this emerging mobility infrastructure using an immersive VR environment. Twenty participants completed a series of six scenarios aimed at understanding customer 'exciters' and 'pain points' within an urban airport. Results and recommendations from this empirical research will help inform the design of all future mobility infrastructure solutions, through improving user experience before the infrastructure is physically deployed. Finally, this paper highlights the benefits of engaging users at an early stage of the design process to ensure that future transport infrastructure will be accessible, easy to navigate and a pleasure to use.

Interactive effects of task load and music tempo on psychological, psychophysiological, and behavioural outcomes during simulated driving.

We examined the interactive effects of task load and music tempo on cognition, affect, cardiac response, and safety-relevant behaviour during simulated driving. Using a counterbalanced, within-subjects design, participants (N = 46) were exposed to fast-, slow-, and no-music conditions at high and low loads in a high-grade simulator. Task load had the most salient effect across a broad swath of variables. For core affect, the Load × Music Condition interaction showed that, under high load, affective arousal scores were higher in the fast-tempo condition vs. slow. A main effect of tempo emerged for the HRV index of SDNN, with fast-tempo music eliciting lower scores than both slow- and no-music conditions. Behavioural data showed a main effect of tempo for risk ratings, with fast-tempo music eliciting the highest scores for a traffic-light trigger. Our findings indicate that drivers in high-load, urban environments should exercise caution in their use of fast-tempo music. Practitioner summary: We examined the interactive effects of task load and music tempo in simulated driving (urban and highway). Cognition, mood, cardiac response, and driving behaviour were assessed. Participants exhibited more risky behaviours in response to fast-tempo music. Drivers should exercise caution in their use of up-tempo music in urban settings.

Psychological, psychophysiological and behavioural effects of participant-selected vs. researcher-selected music in simulated urban driving.

We investigated the effect of participant-selected (PSel) and researcher-selected (RSel) music on urban driving behaviour in young men (N = 27; Mage = 20.6 years, SD = 1.9 years). A counterbalanced, within-subjects design was used with four simulated driving conditions: PSel fast-tempo music, PSel slow-tempo music, RSel music and an urban traffic-noise control. The between-subjects variable of personality (introverts vs. extroverts) was explored. The presence of PSel slow-tempo music and RSel music optimised affective valence and arousal for urban driving. NASA Task Load Index scores indicated that the urban traffic-noise control increased mental demand compared to PSel slow-tempo music. In the PSel slow-tempo condition, less use was made of the brake pedal. When compared to extroverts, introverts recorded lower mean speed and attracted lower risk ratings under PSel slow-tempo music. The utility of PSel slow-tempo and RSel music was demonstrated in terms of optimising affective state for simulated urban driving.

I want to brake free: The effect of connected vehicle features on driver behaviour, usability and acceptance.

This study evaluated the effectiveness and acceptance of four connected vehicle features, i.e. Emergency Electronic Brake Lights (EEBL), Emergency Vehicle Warning (EVW), Roadworks warning (RWW) and Traffic Condition Warning (TCW) which were presented via a mobile phone mounted near the line of sight. A driving simulator study was conducted in which 36 drivers were exposed to different levels of urgent and critical situations. They involved the approach of an emergency vehicle, an emergency braking of a lead vehicle, a roadworks area and a congested section of a road. All these events took place in a simulated motorway scenario. In the EEBL event, the vehicle braking ahead with the brake lights on was either visible or not (between-subjects). Whereas no effect of RWW and TCW were observed on driving behaviour, results showed that drivers who were shown the EEBL warnings had shorter braking and decelerating response times, and a slower mean speed during the events, and this was independent of brake lights visibility. The EVW resulted in participants giving way to the emergency vehicle (i.e. staying on the slow lane instead of overtaking slower vehicles) more frequently than those who did not receive the warning. The mobile phone app was accepted and considered usable. Locating the mobile phone in different locations within the drivers' line of sight (i.e. dashboard, instrument cluster) did not impact significantly neither drivers' attitudes nor behaviour. Additional in-vehicle information systems could enhance safety and allow emergency vehicles to get faster to their destination.

Designing in-vehicle signs for connected vehicle features: Does appropriateness guarantee comprehension?

This paper discusses the design and evaluation of connected and cooperative vehicle in-vehicle sign designs displayed on a mobile phone: Emergency Electronic Brake Lights (EEBL), Emergency Vehicle Warning (EVW), Traffic Condition Warning, and Road Works Warning. Appropriateness and comprehension of each design alternative were assessed using quantitative (i.e. Likert scales) and qualitative (i.e. open-ended questions) methods. Forty-four participants took part in the study and were shown twelve dashboard camera videos presenting a total of eleven designs alternatives, displayed with or without a legend. Despite their appropriateness, EEBL and EVW signs displayed with a legend were better comprehended and less ambiguous than those displayed without a legend. Moreover, displaying a legend below the signs to warn drivers of an emergency braking ahead was efficient in low visibility condition and could potentially increase safety in critical situations.

Fully Automated Driving: Impact of Trust and Practice on Manual Control Recovery.

OBJECTIVE: An experiment was performed in a driving simulator to investigate the impacts of practice, trust, and interaction on manual control recovery (MCR) when employing fully automated driving (FAD). BACKGROUND: To increase the use of partially or highly automated driving efficiency and to improve safety, some studies have addressed trust in driving automation and training, but few studies have focused on FAD. FAD is an autonomous system that has full control of a vehicle without any need for intervention by the driver. METHOD: A total of 69 drivers with a valid license practiced with FAD. They were distributed evenly across two conditions: simple practice and elaborate practice. RESULTS: When examining emergency MCR, a correlation was found between trust and reaction time in the simple practice group (i.e., higher trust meant a longer reaction time), but not in the elaborate practice group. This result indicated that to mitigate the negative impact of overtrust on reaction time, more appropriate practice may be needed. CONCLUSIONS: Drivers should be trained in how the automated device works so as to improve MCR performance in case of an emergency. APPLICATION: The practice format used in this study could be used for the first interaction with an FAD car when acquiring such a vehicle.