Road users rarely use explicit communication when interacting in today’s traffic: implications for automated vehicles

Abstract

To be successful, automated vehicles (AVs) need to be able to manoeuvre in mixed traffic in a way that will be accepted by road users, and maximises traffic safety and efficiency. A likely prerequisite for this success is for AVs to be able to communicate effectively with other road users in a complex traffic environment. The current study, conducted as part of the European project interACT, investigates the communication strategies used by drivers and pedestrians while crossing the road at six observed locations, across three European countries. In total, 701 road user interactions were observed and annotated, using an observation protocol developed for this purpose. The observation protocols identified 20 event categories, observed from the approaching vehicles/drivers and pedestrians. These included information about movement, looking behaviour, hand gestures, and signals used, as well as some demographic data. These observations illustrated that explicit communication techniques, such as honking, flashing headlights by drivers, or hand gestures by drivers and pedestrians, rarely occurred. This observation was consistent across sites. In addition, a follow-on questionnaire, administered to a subset of the observed pedestrians after crossing the road, found that when contemplating a crossing, pedestrians were more likely to use vehiclebased behaviour, rather than communication cues from the driver. Overall, the findings suggest that vehicle-based movement information such as yielding cues are more likely to be used by pedestrians while crossing the road, compared to explicit communication cues from drivers, although some cultural differences were observed. The implications of these findings are discussed with respect to design of suitable external interfaces and communication of intent by future automated vehicles.

Learning to interpret novel eHMI: The effect of vehicle kinematics and eHMI familiarity on pedestrians' crossing behaviour

“…Most of the crossings were made either when the approaching vehicle was more than 42.5 m away, or when the vehicle had come to a near-(between 2.5 -5 m away) or complete-(2.5 m away) stop. These bimodal crossing patterns have been observed in previous simulation models and test-track studies (Giles et al, 2019;, Markkula et al, 2018Schneemann & Gohl., 2016), and support suggestions that the vehicle does not need to come to a full stop for a crossing pedestrian (Lee et al, 2020). This bimodal crossing pattern also suggests that pedestrians were more comfortable crossing the road either when the vehicle was quite far away, or waited until the yielding behaviour of the vehicle was more prominent, i.e.…”

“…For example, many studies on pedestrian-vehicle interactions suggest that pedestrians typically use implicit cues from the vehicle, such as its deceleration profile, to help with their crossing decisions (e.g. Ackermann et al, 2019a;Petzoldt et al, 2018;Šucha et al, 2017;Varhelyi, 1998;Wang et al, 2014;Dey & Terken, 2017;Lee et al, 2020). However, as highlighted above, humans are not very good at identifying subtle changes in kinematic behaviour, especially if the vehicle is far away.…”

I See Your Gesture: A VR-Based Study of Bidirectional Communication between Pedestrians and Automated Vehicles

“…Based on an analysis of communication between road users in today's traffic, Lee et al [22] concluded that road users rarely use explicit communication such as hand gestures. ey also pointed out that "there may be limited requirement for automated vehicles to adopt explicit communication solutions."…”

“…Schieben et al [17] provided a framework for communication between AVs and other road users and showed that various forms of interaction are conceivable, of which eHMIs are one. Other communication strategies include the use of the infrastructure, the design of the vehicle shape, and the AV movements themselves (the latter is also known as implicit communication [18][19][20][21][22]). Moreover, the paper by Schieben et al [17] makes clear that eHMIs do not necessarily have to show the AV's state and intentions.…”

Space Invaders: Pedestrian Proxemic Utility Functions and Trust Zones for Autonomous Vehicle Interactions

“…Interview responses and observations showed that pedestrians use to understand 'some forms of movement from the vehicle as communicating a message'. For example, [15] and [47] showed evidence that such implicit signalling through speed and positioning are the main form of signalling used in road-crossing interactions, as explicit forms of sig-nalling such as hand gestures and facial expressions are not often used.…”