Comparing implicit communication via longitudinal driving dynamics: A cross-cultural study in Germany and the UK

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.