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• Empirical test of the psychometric properties of the Driving Anger Scale (DAS) for German drivers. • Examination of the relationships of driving anger with general anger experience and expression. • Relationships between driving anger and demographic variables. • International comparison of driving anger for drivers from different countries. In 1994, Deffenbacher et al. published the Driving Anger Scale (DAS), a tool for assessing a driver's propensity to experience anger in road traffic. Since then, much research has used this scale to measure the driving anger experienced in various countries around the world. This study examines the scale's validity for German drivers. It also relates their experiences of anger while driving to their experiences and expressions of anger in general, as well as to certain demographic variables. In addition, it compares German drivers' experiences of driving anger to those reported by drivers from other countries. We distributed a German version of the DAS and the State-Trait Anger Expression Inventory (STAXI) to a sample of 1136 German drivers. Results showed that a 22-items version of the DAS with six factors produced good fit indices for German drivers. Furthermore, data analysis revealed small to moderate significant relationships between German drivers' driving anger experiences and their experiences and expressions of anger in general, underlining the idea that driving anger is a personality characteristic that is related to one's general experience and expression of anger. Finally, German drivers' driving anger experiences differed from those of drivers from other countries in that German drivers reported less driving anger than drivers from Spain and New Zealand, comparable levels to those from Turkey, Malaysia, and the United States, and more driving anger than drivers from France, Australia, China, and the United Kingdom. In addition, discourteous driver actions and hostile gestures consistently triggered highest driving anger ratings whereas police presence was rated lowest. Given these results, we conclude that the DAS can be applied to German drivers in its modified version. [ABSTRACT FROM AUTHOR]

• Pedestrians felt more aroused with larger highly automated vehicles (HAVs) than smaller HAVs. • Higher trust ratings were reported for larger HAVs with static eHMI compared to no eHMI, while the opposite was true for smaller HAVs. • Shorter crossing initiation times when pedestrians interacted with HAVs through dynamic eHMI, which signals automation status and yielding intent. • Pedestrians felt safer and trusted HAVs more with dynamic eHMIs compared to static or no eHMIs. • In non-matching conditions, pedestrians showed more negative evaluations of trust, perceived safety, and affective responses than in matching. Highly automated vehicles (HAVs) will soon be introduced into mixed urban traffic. Pedestrians might have an idea of HAVs. Nevertheless, they probably have never interacted with them before. Moreover, pedestrians will not be able to communicate with HAVs like they are used to with manual vehicles. External human–machine interfaces (eHMIs) are possible design solutions for HAVs to ensure safe interaction with other road users. Light-based eHMIs positively affected pedestrians' trust ratings, perceived safety, and willingness to cross. However, previous studies often neglected the effect of vehicle size, although larger-sized HAVs could be potentially perceived as the more significant threat. Additionally, the relationship between vehicle kinematics and eHMIs for differently sized HAVs remains an underexplored research topic. This study investigated the effects of vehicle size (small vs. large), eHMI state (dynamic eHMI vs. static eHMI vs. no eHMI), and vehicle kinematics (yielding vs. non-yielding) on pedestrian crossing behavior and their subjective assessment. In virtual reality, we created a shared space traffic scenario, in which the eHMI and vehicle kinematics matched or did not match. For yielding conditions, the results showed that participants felt more aroused with larger HAVs than with smaller HAVs. Moreover, pedestrians initiated their crossing significantly earlier when both vehicle sizes had a dynamic eHMI compared to a static eHMI vs. no eHMI. Additionally, pedestrians evaluated a dynamic eHMI with higher trust ratings, higher perceived safety, and more positive affective reactions. The results manifested that the use of dynamic eHMIs can effectively enhance pedestrian-vehicle communication with a large and a small HAV. For non-matching conditions, the participants tended to rely on the vehicle kinematics for both vehicle sizes. Overall, the study highlighted the potential of eHMIs for pedestrian interactions with HAVs of varying sizes when they are well-coordinated with the vehicle kinematics, aiming to enhance safety and efficiency in mixed-traffic environments. [ABSTRACT FROM AUTHOR]

• Transparency information can be used to improve passengers' experience when facing minimal risk maneuvers in highly automated vehicles (HAV). • Transparent design of an internal Human-Machine Interface (iHMI) has positive influence on passengers' subjective understanding of the Automated Driving System (ADS). • Usability is not negatively affected by the additional information hinting that it is perceived as relevant by passengers. • When time pressure is applied to passengers, there is specific informational need, like delay and arrival times. • Results point towards different informational needs that are specific to context and situation indicating potential benefits of adaptable interfaces. In Highly Automated Vehicles (HAVs) without operators on-board, user interaction with the vehicle automation plays an important role for a safe and inclusive use of these services. Especially when Minimal Risk Maneuvers (MRM) are performed by the system, passengers are faced with uncertain situations. A possibility to deepen passenger's understanding and predictability of these systeḿs and reduce their uncertainties is to enhance automation transparency. However, literature shows a lack regarding enhancing system transparency of HAVs during MRMs. Therefore, we investigated the impact of "observability" and "reasoning" as transparency influencing factors. In an online study, participants evaluated multiple internal Human-Machine Interfaces (iHMI) as shuttle passengers. The presented iHMIs varied regarding their level of transparency by giving different information about what the vehicle's "perception" and its "reasoning" is. Results show significant differences in the passengers' understanding between different iHMI variants providing evidence that information regarding the "perception" and "reasoning" of HAVs enhance system transparency. Results of the study may provide first insights into passengers' informational needs when using HAV. They highlight the potential benefits of system transparency when designing interfaces for HMIs of automated vehicles. [ABSTRACT FROM AUTHOR]

• Empirical development of the Cycling Anger Scale (CAS). • The CAS is the first measure to assess cycling anger in traffic. • Test of the scale's structural stability with two different samples. • Examination of the CAS's convergent validity with DAS and STAXI. • Relations between cycling anger, demographics, and self-reported cycling behavior. Research on emotions in road traffic has focused on car drivers rather than on cyclists. However, cyclists experience cycling anger and its consequences as vulnerable road users, i.e., without having a car-like protection zone around them. To address the issue of cycling anger, we suggest a psychological measure assessing cyclists' anger experiences in traffic, the Cycling Anger Scale (CAS). This questionnaire assesses cyclists' anger experiences in interaction with their cycling environment. A principal component analysis and a following confirmatory factor analyses with two different samples proposed a 14 items questionnaire solution with four subscales: police interaction, car interaction, cyclist interaction, and pedestrian interaction. Alpha reliabilities were acceptable to good. The CAS correlated significantly with the Driving Anger Scale (DAS) for car drivers and with the general State-Trait Anger Expression Inventory (STAXI) suggesting convergent validity. Additionally, we examined the relations between cycling anger, demographics, and self-reported cycling behavior. We conclude that the CAS provides a complementary efficient instrument for measuring cycling anger in road traffic. [ABSTRACT FROM AUTHOR]

Highlights • Focus groups on anger events in cycling revealed 208 unique cycling anger events. • In a diary study, 54 unique cycling anger events were reported, therein seven new ones. • Most cycling anger events were related to car drivers’ reckless and negligent behaviours. • Inconsiderate pedestrians and lacking infrastructure were also reported often. • Strongest cycling anger was found for interactions with car drivers and pedestrians. Abstract Previous research shows that anger and aggression among road users lead to maladjusted driving and a higher risk of accidents. Especially cyclists as vulnerable road users have a high risk of being injured if they are involved in accidents. This paper examines reasons for cycling anger in two studies. The first study aimed at identifying anger provoking events. Seventy-three cyclists were invited to discuss anger provoking events in a focus group setting. These events were rated regarding their anger intensity, clustered within focus groups, and aggregated across all groups. The first study revealed 208 unique cycling anger provoking events of varying anger intensity that were summarized in six clusters. The second study aimed at validating these anger provoking events, the ratings, and the clusters. Here, 129 participants were asked to complete a four-time point diary study (over the course of ten days), in which they registered all anger provoking events that they experienced while cycling. The results of this study validated most of the anger provoking events of the first study. Both studies show that most anger provoking events are related to conflicts between cyclists with other road users like car drivers and pedestrians. Moreover, conflicts with car drivers seem to cause stronger anger among cyclists than conflicts with other cyclists or pedestrians. Implications for further research and the planning of road infrastructure are discussed. [ABSTRACT FROM AUTHOR]

In this study the location of vehicle to vehicle distance thresholds for self-reported subjective risk and comfort was researched. Participants were presented with ascending and descending time headway sequences in a driving simulator. This so called method of limits of ascending and descending stimuli (Gouy, Diels, Reed, Stevens, & Burnett, 2012) was refined to efficiently determine individual thresholds for stable time headways with a granularity of 0.1 s. Time headway thresholds were researched for 50, 100, and 150 km/h in a city, rural, and highway setting. Furthermore, thresholds for self-driving (level 0 automation: NHTSA, 2013) were compared with thresholds for the experience of subjective risk and comfort in assisted driving, similar to adaptive cruise control (level 1 automation). Results show that preferred individual time headways vary between subjects. Within subjects however, time headway thresholds do not significantly differ for different speeds. Furthermore we found that there was no significant difference between time headways of self-driving and distance-assisted driving. The relevance of these findings for the development of adaptive cruise control systems, autonomous driving and driver behavior modelling is discussed. [ABSTRACT FROM AUTHOR]

There is no agreement on the relation between driving parameters and drivers' subjective states. A linear as well as a threshold relationship for different subjective variables and driving parameters has been put forward. In this study we investigate the relationship between time headway and the ratings of risk, task difficulty, effort, and comfort. Knowledge about this interrelation may advance the development of adaptive cruise control and autonomous driving and can add to the discussion about driver behavior models. An earlier study (Lewis-Evans, De Waard, & Brookhuis, 2010) found a threshold effect for drivers' ratings of subjective variables for time headways between 0.5 and 4.0 s at a speed of 50 km/h. This study aims to replicate the threshold effect and to expand the findings to time headways at different speeds. A new measure for criticality was added as a categorical variable, indicating the controllability of a driving situation to give indications for the appliance of time headway in adaptive cruise control systems. Participants drove 24 short routes in a driving simulator with predefined speed and time headway to a leading vehicle. Time headway was varied eightfold (0.5-4 s in 0.5 s increments) and speed was varied threefold (50, 100, 150 km/h). A threshold effect for the ratings of risk, task difficulty, effort, and comfort was found for all three different speeds. Criticality proved to be a useful variable in assessing the preferred time headway of drivers. [ABSTRACT FROM AUTHOR]

• Well-coordinated interplay of eHMI and vehicle kinematics increased trust, perceived safety, and affective valence in a real-world setting. • Pedestrians initiated crossings earlier with dynamic eHMI, which gave information about the vehicle automation status and yielding intent. • Dynamic eHMI led to a higher perceived trust and a higher perceived safety. • Presence of eHMIs did not affect crossing duration. • Use of LiDAR sensor data for the controlled eHMI activation. Highly automated vehicles (HAVs) will interact with pedestrians in urban environments. This requires efficient communication tools to ensure mutual understanding. Past research showed that pedestrians mostly used vehicle kinematics to communicate with vehicles, e.g., the vehicle's speed and distance. However, pedestrians required further explicit communication signals when the traffic situation was ambiguous. Light-band external human–machine interfaces (eHMIs) transmit additional explicit communication signals to pedestrians, e.g., the vehicle's yielding intent. To this point, the precise interplay of vehicle kinematics and eHMIs for HAVs has not yet been determined. Nevertheless, previous research showed that combining both means of communication has great potential to increase pedestrian perceived safety and to ensure a safe interaction. Only a little research used real vehicle studies to investigate the interaction between pedestrians and HAVs in a close-to-reality experimental setting. However, this would ensure the transferability of experimental results to future urban traffic. Therefore, this study aimed to address this research gap by investigating the effects of vehicle kinematics, eHMIs, and their interplay in a real-world pedestrian crossing on pedestrians' behaviors and subjective evaluations. In this field experiment, we applied a light-band eHMI on a Wizard-of-Oz test vehicle, an actual vehicle instructed as an HAV. We investigated the effects of vehicle kinematics (early yielding vs. late yielding) and the eHMI status (no eHMI, static eHMI, dynamic eHMI) on pedestrians' crossing behavior and subjective evaluation in a low-speed real-world setting. The static eHMI displayed the vehicle automation status by a static illuminated eHMI. The dynamic eHMI conveyed the automation status and the vehicle's yielding intent. This study focused particularly on the interplay of vehicle kinematics and eHMI status. We assumed that the crossing initiation was shorter when a dynamic eHMI was combined with an early yielding compared to a late yielding in this real-world setting. Moreover, we hypothesized that pedestrians' subjective evaluations are more positive for a well-coordinated interplay of eHMI and vehicle kinematics. The results showed that pedestrians initiated their crossing earlier with dynamic eHMI vs. no eHMI or static eHMI. Furthermore, they perceived a dynamic eHMI as safer and more trustworthy compared to no eHMI or a static eHMI. Combining an early yielding and dynamic eHMI increased participants' perceived safety of the vehicle behavior and trust and improved pedestrians' affective evaluations compared to a late yielding with dynamic eHMI. Overall, this real vehicle study highlighted the importance of implicit and explicit communication signals and their well-coordinated interplay for pedestrians' future interactions with HAVs in a real-world setting. [ABSTRACT FROM AUTHOR]

• Light-based eHMIs for automated car and automated bus were evaluated. • Pedestrians perceived interaction with automated bus as less safe vs. automated car. • Higher perceived safety when both vehicles were equipped with dynamic eHMIs. • Dynamic eHMIs also contributed to a more positive affective evaluation. • Higher usability ratings for the automated vehicles with dynamic vs. static eHMI. Differently sized automated vehicles (AVs) will enter the roads of tomorrow and will interact with other road users. Pedestrians as vulnerable road users heavily rely on the communication with other road users, especially for the interaction with larger vehicles, as miscommunication pose a high risk. Therefore, AVs need to provide communication abilities to safely interact with pedestrians. This study's focus was on the explicit communication which is highly relevant in low-speed and low-distance traffic scenarios to clarify misunderstandings before they result in accidents. External human-machine interfaces (eHMIs) placed on the outside of AVs can be used as a communication tool to explicitly inform the surrounding traffic environment. Although research manifested effects of vehicle size on pedestrians' perceived safety and crossing behavior, little research about the eHMI design for differently sized AVs exists. This experimental online study (N = 155) aimed at investigating the application of a light-based eHMI on two differently sized AVs (car, bus) by focusing on the overall goal of ensuring traffic safety in future traffic. The light-based eHMI showed different communication strategies, i.e., a static eHMI and three dynamic eHMIs. The results revealed that an automated car was perceived as safer and affectively rated as more positive compared to an automated bus. Nevertheless, no significant differences were found between the two AVs in terms of the eHMI communication. A dynamic eHMI was perceived as safer and evaluated affectively as more positive compared to a static eHMI or no eHMI for both AVs. In conclusion, the use of a light-based eHMI had a positive effect on pedestrians' interaction with an automated car and an automated bus and, therefore, could contribute to the overall traffic safety in this study. Implications for the design of eHMIs for differently sized AVs were discussed. [ABSTRACT FROM AUTHOR]

• First-time investigation of light-band eHMIs for pedestrians' interaction with highly automated vehicles in Japan. • Light-band eHMIs contributed to pedestrians' willingness to cross, trust and perceived safety in Japan. • Similar positive findings of light-band eHMIs when comparing pedestrians' subjective evaluation in Japan and Germany. • Identification of possible side effects of malfunctioning eHMIs: Japanese relied on eHMI, although the eHMI contradicted the vehicle kinematics. In the near future, pedestrians will face highly automated vehicles on the roads. Highly automated vehicles (HAVs) should have safety-enhancing communication tools to guarantee traffic safety, e.g., vehicle kinematics and external human–machine interfaces (eHMIs). Pedestrians, as highly vulnerable road users, depend on communication with HAVs. Miscommunication between pedestrians and HAVs could quickly result in accidents, and this, in turn, could cause severe impairments for pedestrians. Light-band eHMIs have the potential to enhance traffic safety. However, eHMIs have been less explored in Japan so far. As a first-time approach, this experimental online study shed light on the effect of a light-band eHMI on Japanese pedestrians (N =99). In short video sequences, the participants interacted with two differently sized HAVs equipped with light-band eHMI. We investigated the effect of vehicle size (small vs. large), eHMI status (no eHMI vs. static eHMI vs. dynamic eHMI), and vehicle kinematics (yielding vs. non-yielding) on pedestrians' willingness to cross, trust, and perceived safety. To investigate possible side effects of eHMIs, we also included experimental conditions in which the eHMI mismatched the vehicle's kinematics. Results revealed that Japanese were more willing to cross the street and indicated higher trust- and safety ratings when they received information about the vehicle's intention and automation status (dynamic eHMI) compared to when they received no information (no eHMI) or only about the vehicle automation status (static eHMI). Surprisingly, Japanese participants tended to rely on the eHMI when there was mismatching information between eHMI and vehicle kinematics. Overall, we concluded that light-band eHMIs could contribute to a safe future interaction between pedestrians and HAVs in Japan under the requirement that the eHMI is in accordance with vehicle kinematics. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Maladaptive driving is an important source of self-inflicted accidents and this driving style could include high speeds, speeding violations, and poor lateral control of the vehicle. The literature suggests that certain groups of drivers, such as novice drivers, males, highly motivated drivers, and those who frequently experience anger in traffic, tend to exhibit more maladaptive driving patterns compared to other drivers. Remarkably, no coherent framework is currently available to describe the relationships and distinct influences of these factors. Method: We conducted two studies with the aim of creating a multivariate model that combines the aforementioned factors, describes their relationships, and predicts driving performance more precisely. The studies employed different techniques to elicit emotion and different tracks designed to explore the driving behaviors of participants in potentially anger-provoking situations. Study 1 induced emotions with short film clips. Study 2 confronted the participants with potentially anger-inducing traffic situations during the simulated drive. Results: In both studies, participants who experienced high levels of anger drove faster and exhibited greater longitudinal and lateral acceleration. Furthermore, multiple linear regressions and path-models revealed that highly motivated male drivers displayed the same behavior independent of their emotional state. The results indicate that anger and specific risk characteristics lead to maladaptive changes in important driving parameters and that drivers with these specific risk factors are prone to experience more anger while driving, which further worsens their driving performance. Driver trainings and anger management courses will profit from these findings because they help to improve the validity of assessments of anger related driving behavior. [Copyright &y& Elsevier]

Abstract: Statistics indicate that in 2011 more than 2,3 Million traffic accidents occurred on German roads inflicting almost 4100 casualties. A contributing factor for accidents is inappropriate driving behaviour (e.g., risky or aggressive driving or delayed reactions) due to the drivers’ strong emotional state. Several situational factors such as goal congruence, goal relevance and blame have been examined and are considered responsible for the nature and intensity of the emotions experienced. However, the impact – and especially the interaction – of these situational factors on emotions experienced in traffic situations are not yet sufficiently clear. Therefore two consecutive studies have concentrated on this question. The participants had to rate emotions they would experience in traffic scenarios, which were presented as short texts in an online-questionnaire. A distinct combination of the situational factors served as a framework for each of the scenarios. In order to assess an extensive variety of emotions, two different versions of the Geneva Emotion Wheel were used. In both studies different combinations of goal congruence, goal relevance and blame influenced participants’ emotions. Anger, anxiety and positive feelings such as hope, relief and satisfaction were related to the situational factors. The second study showed that the development of pride, guilt and shame could also be traced back and associated with the appraisal of those situational characteristics. [Copyright &y& Elsevier]