Communicating Intent of Automated Vehicles to Pedestrians

Abstract

While traffic signals, signs, and road markings provide explicit guidelines for those operating in and around the roadways, some decisions, such as determinations of “who will go first,” are made by implicit negotiations between road users. In such situations, pedestrians are today often dependent on cues in drivers’ behavior such as eye contact, postures, and gestures. With the introduction of more automated functions and the transfer of control from the driver to the vehicle, pedestrians cannot rely on such non-verbal cues anymore. To study how the interaction between pedestrians and automated vehicles (AVs) might look like in the future, and how this might be affected if AVs were to communicate their intent to pedestrians, we designed an external vehicle interface called automated vehicle interaction principle (AVIP) that communicates vehicles’ mode and intent to pedestrians. The interaction was explored in two experiments using a Wizard of Oz approach to simulate automated driving. The first experiment was carried out at a zebra crossing and involved nine pedestrians. While it focused mainly on assessing the usability of the interface, it also revealed initial indications related to pedestrians’ emotions and perceived safety when encountering an AV with/without the interface. The second experiment was carried out in a parking lot and involved 24 pedestrians, which enabled a more detailed assessment of pedestrians’ perceived safety when encountering an AV, both with and without the interface. For comparison purposes, these pedestrians also encountered a conventional vehicle. After a short training course, the interface was deemed easy for the pedestrians to interpret. The pedestrians stated that they felt significantly less safe when they encountered the AV without the interface, compared to the conventional vehicle and the AV with the interface. This suggests that the interface could contribute to a positive experience and improved perceived safety in pedestrian encounters with AVs – something that might be important for general acceptance of AVs. As such, this topic should be further investigated in future studies involving a larger sample and more dynamic conditions.

Pedestrian Trust in Automated Vehicles: Role of Traffic Signal and AV Driving Behavior

“…Traditional methods of explicit communication in HDVs include indicator lamps, brake lamps, and horns. Current research on AV explicit communication primarily explores the efficacy of additional specialized interfaces such as light-emitting diode message boards, light-emitting diode lights, interactive head lamps, etc., in conveying vehicle intent in the absence of human drivers (Chang et al, 2017(Chang et al, , 2018Habibovic et al, 2018;Mahadevan et al, 2018). Although these approaches are valuable and insightful, there is currently no one standard communication interface.…”

Standardized Test Procedure for External Human–Machine Interfaces of Automated Vehicles

“…Results are inconclusive regarding the benefit of using an eHMI to signal maneuver intentions of automated vehicles. In some studies, communicating the maneuver intention of the automated vehicle increased the subjective ratings of interaction partners in comparison to interactions without an eHMI [9][10][11][12]. In other studies, such eHMI concepts did not have any impact on pedestrians' perceived trust and safety [1] or even had a negative effect on pedestrians' workload during interactions with automated vehicles [13].…”

“…Moreover, it is still unclear whether communicating the vehicle's automation status with eHMI systems improves the subjective experiences of interaction partners. On the one hand, eHMI systems that signaled the automation status with light-emitting diode (LED) strips had a positive effect on pedestrians' emotional experience [11] and perceived safety [12] compared to interactions without an eHMI. On the other hand, other studies did not reveal an impact of communicating the automation status on pedestrians' perceived stress [14] and perceived safety [1], such as on cyclists' reported behavior [15].…”

“…Previous research has used very different methodological approaches and has had methodological limitations. Methodological limitations include a lack of behavioral measurements [8,9], small sample sizes [12,13], and vague result reports [4,20]. In some studies, participants evaluated the eHMI after they had received a thorough briefing and explanation of the signal meanings [9,11,12].…”

“…Methodological limitations include a lack of behavioral measurements [8,9], small sample sizes [12,13], and vague result reports [4,20]. In some studies, participants evaluated the eHMI after they had received a thorough briefing and explanation of the signal meanings [9,11,12]. In other studies, participants reported their subjective ratings of the situation even though some of them had not even perceived the eHMI [1,14].…”