People with more misconceptions about automated vehicles might be more positive toward them

Automated vehicle (AV) technology is likely to influence transportation, mobility, and society dramatically. The year 2020 was a horizon year for the AV, as manufacturers expected commercial AVs to be available to the general market. However, we experienced one cycle of hyperbole for these “self-driving” cars, which are still unavailable to consumers. Meanwhile, many persistent beliefs about this technology are factual or arguable misconceptions. However, the public attitude literature rarely examines public misconceptions of AVs. Thus, we explored the prevalence of three misconceptions: “AVs are already available in the market,” “AVs do not need to be driven manually at all,” and “Mature business models for AVs have been established.” We investigated these misconceptions’ correlations with several cognitive (i.e., benefit and risk perceptions), affective (i.e., positive and negative affect), and behavioral components (i.e., behavioral intention and willingness to pay) of attitudes and trust in AVs. Our online survey in China (N = 1,026) indicated that more than 70% of participants hold one or more of the three misconceptions, with one-third believing that AVs are already available in the market. Furthermore, participants believing one or more of the three misconceptions were more positive regarding specific attitudinal factors (e.g., those who believed that AVs are already available reported greater behavioral intention to use and willingness to pay for AVs than those who rejected this misbelief). This finding indicates that people who are more wrong about AVs might be more positive toward AVs. We need effective and accurate public communication to dispel public misconceptions about AVs and build rational expectations.     

Behavioral adaptations of human drivers interacting with automated vehicles

Advancements in technology are bringing automated vehicles (AVs) closer to wider deployment. However, in the early phases of their deployment, AVs will coexist and frequently interact with human-driven vehicles (HDVs). These interactions might lead to changes in the driving behavior of HDVs. A field test was conducted in the Netherlands with 18 participants focusing on gap acceptance, car-following, and overtaking behaviors to understand such behavioral adaptations. The participants were asked to drive their vehicles in a controlled environment, interacting with an HDV and a Wizard of Oz AV. The effects of positive and negative information regarding AV behavior on the participants’ driving behavior and their trust in AVs were also studied. The results show that human drivers adopted significantly smaller critical gaps when interacting with the approaching AV as compared to when interacting with the approaching HDV. Drivers also maintained a significantly shorter headway after overtaking the AV in comparison to overtaking the HDV. Positive information about the behavior of the AV led to closer interactions in comparison to HDVs. Additionally, drivers showed higher trust in the interacting AV when they were provided with positive information regarding the AV in comparison to scenarios where no information was provided. These findings suggest the potential exploitation of AV technology by HDV drivers.     

The effects of adaptive cruise control (ACC) headway time on young-experienced drivers' overtaking tendency in a driving simulator

The preference to maintain a certain desired speed is perhaps the most prevalent explanation for why a driver of a manually driven car decides to overtake a lead vehicle. Still, the motivation for overtaking is also affected by other factors such as aggressiveness, competitiveness, or sensation-seeking caused by following another vehicle. Whether such motivational factors for overtaking play a role in partially automated driving is yet to be determined. This study had three goals: (i) to investigate whether and how a driver's tendency to overtake a lead vehicle changes when driving a vehicle equipped with an adaptive cruise control (ACC) system. (ii) To study how such tendencies change when the headway time configuration of the ACC system varies. (iii) To examine how the manipulation of the speed and speed variance of the lead vehicle affect drivers' tendencies to overtake a lead vehicle. We conducted two different experiments, where the second experiment followed the first experiment's results. In each experiment, participants drove three 10–12 min simulated drives under light traffic conditions in a driving simulator under manual and level one (L1) automation driving conditions. The automation condition included an ACC with two headway time configurations. In the first experiment, it was 1 sec and 3 secs, and in the second, it was 1 sec and 2 secs. Each drive included six passing opportunities representing three different speeds of the lead vehicle (−3 km/h, +3 km/h, +6 km/h relative to the participant), with or without speed variance. Results show that drivers tended to overtake a lead vehicle more often in manual mode than in automated driving modes. In the first experiment, ACC with a headway time of 1 sec led to more overtaking events than ACC with 3 secs headway time. In addition, the relative speed of the lead vehicle and its speed variability affected overtaking tendencies. In the second experiment, the relative speed of the lead vehicle and its speed variability affected overtaking tendencies only when interacting with each other and with driving configuration. When the speed of the lead vehicle was +3 km/h and included variability, more overtaking events occurred in manual mode than both automation modes. This work has shown that driving with ACC might help reduce overtaking frequencies and more considerable when the headway time is set to 3 secs.     

Exploring the acceptance of connected and automated vehicles: Focus group discussions with experts and non-experts in transport

The successful deployment of connected and automated vehicles (CAVs) will largely depend on public opinion. Expectations and concerns are essential components driving the speed of market uptake and final adoption of these technologies. We have studied user expectations and concerns, as well as their provenance, by conducting a series of Focus Group (FG) discussions with transport area experts and non-expert participants, in Italy, Germany, and Spain. Together with user acceptance, potential advantages and disadvantages that CAVs may bring at a societal level were explored. Results show that benefits like increased safety and accessibility and improved travel experience for both driver and passengers could support CAVs’ deployment. Nevertheless, a variety of concerns were raised during the discussions, related to privacy, responsibility in case of an accident, and increase in maintenance and repair costs. These aspects could significantly hamper or delay CAVs acceptability and need to be carefully considered by stakeholders. The reported insights from the FG discussions and the fact that some participants noted positive changes of their initial idea of CAVs due to their participation in the discussion, exemplify the importance of citizen engagement activities to address mobility challenges.     

Investigating explanations in conditional and highly automated driving: The effects of situation awareness and modality

With the level of automation increases in vehicles, such as conditional and highly automated vehicles (AVs), drivers are becoming increasingly out of the control loop, especially in unexpected driving scenarios. Although it might be not necessary to require the drivers to intervene on most occasions, it is still important to improve drivers’ situation awareness (SA) in unexpected driving scenarios to improve their trust in and acceptance of AVs. In this study, we conceptualized SA at the levels of perception (SA L1), comprehension (SA L2), and projection (SA L3), and proposed an SA level-based explanation framework based on explainable AI. Then, we examined the effects of these explanations and their modalities on drivers’ situational trust, cognitive workload, as well as explanation satisfaction. A three (SA levels: SA L1, SA L2 and SA L3) by two (explanation modalities: visual, visual + audio) between-subjects experiment was conducted with 340 participants recruited from Amazon Mechanical Turk. The results indicated that by designing the explanations using the proposed SA-based framework, participants could redirect their attention to the important objects in the traffic and understand their meaning for the AV system. This improved their SA and filled the gap of understanding the correspondence of AV’s behavior in the particular situations which also increased their situational trust in AV. The results showed that participants reported the highest trust with SA L2 explanations, although the mental workload was assessed higher in this level. The results also provided insights into the relationship between the amount of information in explanations and modalities, showing that participants were more satisfied with visual-only explanations in the SA L1 and SA L2 conditions and were more satisfied with visual and auditory explanations in the SA L3 condition. Finally, we found that the cognitive workload was also higher in SA L2, possibly because the participants were actively interpreting the results, consistent with a higher level of situational trust. These findings demonstrated that properly designed explanations, based on our proposed SA-based framework, had significant implications for explaining AV behavior in conditional and highly automated driving.     

Control of impulsive emotional behaviour through implementation intentions

Past research has established that people can strategically enhance or override impulsive emotional behaviour with implementation intentions (Eder, Rothermund, & Proctor, 2010). However, it is unclear whether emotional action tendencies change by intentional processes or by habit formation processes due to repeated enactment of the intention (or both). The present study shows that forming implementation intentions is sufficient to modulate emotional action tendencies. Participants received instructions about how to respond to positive and negative stimuli on evaluation trials but no such trials were actually presented. Results showed that merely intending to approach and avoid affective stimuli influenced emotional action tendencies in a modified affective Simon task in which affective valence was irrelevant. An affective Simon effect (i.e., faster reactions when the valence of the stimulus corresponded with the valence of the movement) was observed when participants intended evaluations with affectively congruent responses (i.e., positive–approach, negative–avoid); in contrast, the effect was reversed in direction when participants planned evaluations with incongruent responses (i.e., positive–avoid, negative–approach). Thus, implementation intentions can regulate implicit emotional responses even in the absence of possible habit formation processes. Implications for dual-system accounts of emotion regulation are discussed.     

Hydrocortisone infusion exerts dose- and sex-dependent effects on attention to emotional stimuli

Glucocorticoid administration has been shown to exert complex effects on cognitive and emotional processing. In the current study we investigated the effects of glucocorticoid administration on attention towards emotional words, using an Affective Go/No-go task on which healthy humans have shown an attentional bias towards positive as compared to negative words. Healthy volunteers received placebo and either low-dose (0.15 mg/kg) or high-dose (0.45 mg/kg) hydrocortisone intravenously during two separate visits in a double-blind, randomized design. Seventy-five minutes post-infusion, the subjects performed tests of attention (Rapid Visual Information Processing [RVIP]), spatial working memory (Spatial Span) and emotional processing (Affective Go/No-go task [AGNG]). On the attention task, performance was impaired under both hydrocortisone doses relative to placebo, though the effect on error rate was not significant after controlling for age; Spatial Span performance was unaffected by hydrocortisone administration. On the AGNG task, relative to the placebo condition the low-dose hydrocortisone infusion decreased response time to emotional words while high-dose hydrocortisone increased response time. In the females specifically, both high and low dose hydrocortisone administration attenuated the normal attentional bias toward positively valenced words. These data suggest that, in healthy women, the modulation of attention by the emotional salience of stimuli is influenced by glucocorticoid hormone concentrations.     

Objective and perceived risk in overtaking: The impact of driving context

The assistance and autonomous performance of overtaking manoeuvres can offer significant safety benefits. The impact of driving context on perceived risk emphasises the benefits of using contextual information to adjust the manoeuvring behaviour. This paper follows a mixed approach, addressing two main objectives: identifying factor combinations related to overtaking crashes (objective risk) and exploring their relationship to perceived risk. Factor combinations were extracted from a multi-year dataset, acquired from the UK in-depth study RAIDS (Road Accident In-depth Studies). Selected factors were used to create motorway overtaking scenarios with different manoeuvring behaviour (pull-out distance, manoeuvre duration, speed) and driving context (day/night, overtaking car/truck), while 237 participants assessed their impact on perceived risk through an online survey. The findings highlight the strong impact of manoeuvre characteristics on perceived risk, mediated or intensified by the driving context. Long pull-out distance and short manoeuvre duration time were preferred; under night conditions, short pull-out distances were perceived as riskier compared to daytime, while the opposite effect appeared for high speed, which was considered safer. The results can inform future research on motorway overtaking safety perception and acceptability, as well as the design of systems that assist or autonomously perform overtaking. Specifically, they can be used as guidelines for incorporating context related information to adjust overtaking behaviour according to user preferences and create a positive passenger experience.     

The impact of a dedicated lane for connected and automated vehicles on the behaviour of drivers of manual vehicles

Connected and automated vehicles (CAVs) are expected to enhance traffic efficiency by driving at shorter time headways, and traffic safety by shorter reaction times. However, one of the main concerns regarding their deployment is the mixed traffic situation, in which CAVs and manually driven vehicles (MVs) share the same road.This study investigates the behavioural adaptation of MV drivers in car-following and lane changing behaviour when they drive next to a dedicated lane (DL) for CAVs and compares that to a mixed traffic situation. The expectation is that in a mixed traffic situation, the behavioural adaptation of MV drivers is negligible due to lower exposure time and scarce platoons, while concentrating the CAVs on one dedicated lane may cause significant behavioural adaptation of MV drivers due to a higher exposure time and conspicuity of CAV platoons.Fifty-one participants were asked to drive an MV on a 3-lane motorway in three different traffic scenarios, in a fixed-base driving simulator: (1) Base, only MVs were present in traffic, (2) Mixed, platoons of 2–3 CAVs driving on any lane and mixed with MVs, (3) DL, platoons of 2–3 CAVs driving only on a DL. The DL was recognizable by road signs and a buffer demarcation which separated the DL from the other lanes. A moderate penetration rate of 43% was assumed for CAVs.During the drives, the car following headways and the accepted merging gaps by participants were collected and used for comparisons of driving behaviour in different scenarios.Based on the results, we conclude that there is no significant difference in the driving behaviour between Base and Mixed scenarios at tested penetration rate, confirming our research expectation. However, in DL scenario, MV drivers drove closer to their leaders specially when driving on the middle lane next to the platoons and accepted shorter gaps (up to 12.7% shorter at on-ramps) in lane changing manoeuvres. Dedicating a lane to CAVs increases the density of CAV platoons on one lane and consequently their conspicuity becomes higher. As a result, MV drivers are influenced by CAV platoons on a DL and imitate their behaviour.The literature suggests that dedicating a lane to CAVs improves the traffic efficiency by providing more possibilities for platooning. This study shows that implementing such a solution will affect the driving behaviour of human drivers. This should be taken into consideration when evaluating the impacts of dedicated lanes on traffic efficiency and traffic safety.