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• Cooperative behaviors among road users, such as predicting and compensating for another road user's mistakes, were investigated. • A 12-day traffic observation with stationary mounted cameras was conducted at an urban T-intersection in Germany, where cars with priority appearing from the right encountered cars or bikes without priority coming from the left. • Cyclists were found to disregard the "priority-to-the-right" rule more often than motorists. • Road users with priority are more likely to yield when turning right and arriving at the intersection later. • Road users who disregard the "priority-to-the-right" rule are more likely to stay near the center of the road, while those who yield tend to move closer to the roadside. The integration of autonomous driving into mixed traffic environments poses unique challenges, especially at unsignalized intersections where communication and cooperation with human road users is necessary. This study addresses a critical research gap by investigating the adherence to the "priority-to-the-right" rule at an urban unsignalized intersection, comparing behavioral patterns of cyclists and motorists. Utilizing stationary mounted cameras, a 12-day traffic observation of an urban T-intersection in Braunschweig, Germany, was conducted. The class and the trajectory of road users as well as their scenarios were identified. In 202 cases, cars appearing from the right (ego, with priority) encountered cars or bikes coming from the left (foe, without priority). The study analyzed the impact of variables, ego's direction, foe's class and lateral position and their arrival time on their passing order through descriptive statistics and logistic regression. The findings reveal that cyclists disregard the "priority-to-the-right" rule more often than motorists. Additionally, road users who have the priority are more likely to yield when turning right, arriving at the intersection later, and encountering an opposing road user who is close to the center of the road. This study highlights the importance of implicit communication in traffic and provides essential benchmarks for developing more human-like autonomous driving systems, capable of interpreting and responding to nuanced road user interactions at unsignalized intersections. [ABSTRACT FROM AUTHOR]

• Link drivers and pedestrians in real-time distributed simulation. • Present driver's bimodal braking strategies. • Identify lateral movements as implicit cues in road user interactions. • Showcase pedestrians' behavioural adaptations to kinematic cues. • Highlight decisions of both actors shaped by time gaps and road infrastructure. As we move towards a future with Automated Vehicles (AVs) incorporated in the current traffic system, it is crucial to understand driver-pedestrian interaction, in order to enhance AV design and optimization. Previous research in this area, which has primarily used naturalistic observations or single-actor virtual reality simulations, has been limited by its inability to draw causal conclusions, also due to a lack of real human–human interactions. Our study addresses these limitations by employing a high-fidelity distributed simulation setup that links drivers in a motion-based simulator with pedestrians in a CAVE-based environment. This method allows for the examination of real-time and reciprocal interactions across a range of road-crossing scenarios. Using thirty-two pairs of drivers and pedestrians, we investigated how different factors, such as the presence of zebra crossings and varying time gaps of the approaching vehicle, influence driver behaviour and pedestrian crossing decisions. The effect of drivers' control of the vehicle during such crossings (e.g., braking behaviour and lateral deviation) on pedestrians' crossing decisions were also analysed. We found that the distribution of drivers' average deceleration values were bimodal, where drivers either markedly yielded to pedestrians, or continued in their path, with very few instances of intermediate behaviour. We also found that pedestrian decisions were seemingly influenced by the different braking strategies adopted by the driver, with pedestrians crossing before the vehicles in response to soft and early, or late and hard braking, while late and soft braking often resulted in the vehicle passing first. We also observed a slight lateral movement of the vehicle away from pedestrians when drivers were not yielding, but more of a lateral deviation towards them when yielding. This may be because drivers subconsciously transfer their walking interaction habits to their driving behaviour, to avoid a collision with pedestrians. Finally, our results showed a stronger influence of these kinematic cues on pedestrian crossing decisions, when compared to zebra crossings. As well as highlighting the value of a novel approach for investigating vehicle–pedestrian interactions, this study illustrates how vehicle cues can assist pedestrian decisions, adding new knowledge in the development of human-like behaviour for future AVs. [ABSTRACT FROM AUTHOR]

• Drivers on slip roads want vehicles on the target lane to decelerate. • Drivers in target lanes rate the behaviour of vehicles on slip roads ambiguously. • AVs are rated identically or even more positively than MVs with identical behaviour. • No different safety distance is kept from automated vehicles. • Results show that cross-border traffic between Germany and UK with AVs is feasible. • Intercultural aspects must still be considered in the development of AVs. To ensure safe and uninterrupted traffic flow, (semi-)automated vehicles must be capable of providing comprehensible and agreeable implicit communication cues to human drivers. This driving simulator study investigated the assessment of implicit communication at a motorway slip road through longitudinal driving dynamics (acceleration, deceleration, and maintaining speed). The second aim of the study was to determine whether expectations of automated vehicles are different from those of human drivers. And thirdly, we investigated whether these findings are country-specific or can be (partially) generalised to other countries. The perception of three means of communication in connection with the presence of a labelling as an automated vehicle (eHMI) was examined in two samples in Germany and England. 27 participants drove from a slip road onto the motorway and interacted with another vehicle. After a stretch on the motorway, they passed a second slip road on which there was a vehicle merging onto the participants lane. This was repeated six times to test all variables. After each situation, the perceived cooperativity and criticality was recorded, as well as the time headway (THW) to the other vehicle. This paper presents the findings from the UK sample and compares them with the German results, which were previously published. Results show, that when the cooperating vehicles are on the slip road, participants from both countries prefer this vehicle to decelerate. However, when participants themselves are on the slip road, expectations for vehicles on the target lane are ambiguous in the UK sample. Except for one aspect (perceived cooperativity of decelerating vehicles on the slip road), the perception of automated vehicles is similar to those of manual drivers. Also, UK participants do not maintain a different safety distance from these vehicles, while this is the case in the German sample. This paper contributes valuable insights into the cross-cultural evaluation of driving dynamics, shedding light on implications for the development and acceptance of automated vehicles. [ABSTRACT FROM AUTHOR]

• Dynamics of turning vehicles as a means of communication were investigated. • Turning maneuvers involve deceleration, even if vehicles do not intend to stop. • A video-based laboratory study was conducted. • Driving dynamics remain the basis of pedestrians' crossing evaluations. Several studies have investigated implicit communication, such as driving dynamics, as a way to communicate vehicle or driver intention to pedestrians, indicating that "good" human driving behavior is sufficient to ensure a subjectively safe crossing, regardless of the vehicle's automation status. Using a video-based laboratory experiment, the present study investigates the extent to which such findings can be transferred to more complex driving maneuvers, such as turning. The results reveal that even in this case, driving dynamics and distance remain the main determinants of crossing decisions and perceived safety. To be able to draw conclusions for vehicle algorithms, more driving maneuvers need to be investigated and analyzed. [ABSTRACT FROM AUTHOR]

• Analysis of the effect of external human machine interface (eHMI), acoustic signal and pitch motion and the combination of both on pedestrianś crossing behavior and safety feeling. • Analysis of actual crossing behavior under real world conditions. • Beneficial effects of eHMI and acoustic signal on participantś crossing decision and safety feeling. Communication between automated vehicles (AVs) and pedestrians is crucial to coordinate traffic maneuvers and hence maintain road safety. Automated driving changes the driver's role to that of a mere passenger, who can perform non-driving related tasks and therefore may not interact with other road users. In this novel traffic environment, both explicit and implicit cues might contribute to an effective communication between AVs and pedestrians by providing relevant information. So far, physical prototypes of AV communication have rarely been evaluated under real world conditions. The few studies managed to do so used a Wizard of Oz technique, where a human operator simulates the behavior of an AV. To measure the communication effectiveness, these studies instructed participants to explicitly state their crossing decision, but not to cross. While safety is assured, the generalizability of the results to pedestrians' actual crossing behavior is unclear. We established a more realistic experimental setup for a Wizard of Oz study that allows pedestrians to actually start crossing while a of simulated AV is approaching. In a Wizard of Oz study, participants (N = 35) interacted with a simulated AV and had to infer its intention. In a fully factorial design, the effects of three different communication cues were explored: an external human-machine interface (eHMI, absent vs. present), an acoustic signal (absent vs. present), and pitch motion (active, normal, or none). The eHMI and acoustic signal were considered as explicit and the pitch motion as implicit cues. Participants were asked to exhibit natural crossing behavior which was captured by two optical tracking systems. Consistently to previous work, explicit AV communication showed a positive effect on pedestrians' crossing behavior and safety feeling. Pedestrians initiated their crossings earlier and reported to feel safer when approaching an AV with an eHMI or an acoustic signal, compared to only having only a pitch motion. There was no main effect of pitch motion on crossing behavior and safety feeling. Nevertheless, there was an interaction between eHMI and active pitch motion. The effect of eHMI on crossing initiation time (CIT) was smaller in combination with an active pitch motion compared to normal pitch conditions. These results underline the importance of implementing appropriate AV communication. [ABSTRACT FROM AUTHOR]

• Analysis of a two-step communication concepts for automated vehicles which provided implicit and explicit communication cues at two distances. • Comparison of two-step and single-step communication concepts. • Beneficial effect of single-step communication concepts on pedestrians' crossing behavior and safety feeling, no further improvements by two-step communication concepts. • Analysis of fixation patterns in pedestrian interactions with automated vehicles. • Consistent pattern of pedestrians' fixation behavior as a function of the automated vehicle's distance. An important challenge of automated vehicles (AV) will be the cooperative interaction with surrounding road users such as pedestrians. One solution to compensate for the missing driver-pedestrian interaction might be explicit communication via external human machine interfaces (eHMIs). Additionally, implicit communication such as a vehicle pitch motion might support AVs when interacting with pedestrians. While previous work explored various explicit and implicit communication cues, these concepts communicated the intention of the AV at one single time point. Currently, empirical findings on two-step communication lack so far. In this study, we empirically test the effect of a two-step AV communication that uses an implicit cue at a long distance and subsequently provides an implicit or explicit cues at a short distance. We compared its efficiency to single-step communication concepts providing implicit or explicit cues at the shorter distance only. To explore whether the right communication cue is used at the right distance, we analyzed pedestrians' fixations while approaching an AV using an eye tracking device. We conducted a virtual reality study (N = 30) with AV communication concept that provided an active pitch motion or an eHMI and compared them with a two-step AV communication concept that provided an additional active pitch motion at a long distance when approaching the pedestrian. Furthermore, we recorded pedestrians' fixation behavior while the AV approached. Consistently to previous work, single-step AV communication showed a beneficial effect on crossing behavior. Pedestrians initiated their crossing earlier while approaching an AV with an active pitch motion or an eHMI compared to the baseline condition. While active pitch motion reduced subjective safety feeling, eHMI increased it. However, the two-step communication concept did not further improve pedestrians' crossing initiation times and their safety feeling. The pattern of fixation behavior differed as a function of AV distance. When the approaching AV was far away, pedestrians exclusively looked at the environment. During the approach, pedestrians gradually fixated the bumper and the hood and only then the windshield of the AV. Hence, it seems to be useful to present an AV intent communication at a certain distance from the pedestrian. These findings posit the importance of considering pedestrians' fixation behavior when developing communication concepts between AVs and pedestrians. [ABSTRACT FROM AUTHOR]

Highlights • Experimental study for a cooperative t-intersection deadlock scenario. • Testing of different approaching behaviours for designing automated vehicles. • In complex situations, drivers prefer to let their cooperation partners drive first. • Explicit Communication signals tend to be given more to the right than to the left. Abstract Mixed traffic between automatic guided cars and human road users makes it necessary to understand cooperative behaviour between road users in order to adapt automated behaviour to human expectations. Road traffic offers various challenges, one being cooperative situations, which are not regulated by law. For example a t-intersection in which one road user is driving straight forward and two road users are turning left. To solve this situation the road users have to cooperate with each other. Different kinds of approaching behaviours in such situations were generated and analyzed according to cooperation readiness, preference to drive first and perceived safety of the situation by means of an experiment. The results show that in complex situations – like the investigated scenario – human road users prefer not to drive first. Additionally a high cooperation readiness of the opposite driver combined with a defensive driving style received higher ratings in the “confidence of passing”. [ABSTRACT FROM AUTHOR]