Understanding the Headless Rider: Display-Based Awareness and Intent-Communication in Automated Vehicle-Pedestrian Interaction in Mixed Traffic

Abstract

Automated vehicles do not yet have clearly defined signaling methods towards other road users, which could complement natural communication practices with human drivers, such as eye contact or hand gestures. In order to establish trust, external human–machine interfaces (eHMIs) have been proposed, but so far, these have not been widely evaluated in natural traffic contexts. This paper presents a user study where 30 participants interacted with a functional display-based visual eHMI for an automated shuttle in mixed urban traffic. Two distinct features were investigated: the communication of (1) its awareness of different obstacles on the road ahead and (2) of its intention to start or to brake. The results indicate that the majority of participants in general regarded eHMIs as necessary for automated vehicles. When reflecting their experience with the eHMIs, about half of the participants experienced an increased comprehension and safety. The combined presentation of obstacle awareness and vehicle intentions helped more participants to understand the shuttle’s behavior than the presentation of obstacle awareness only, but fewer participants regarded this combination of awareness and intent to be safe. The strength of the found effects on subjective responses varied with regard to age and gender.

Blinded windows and empty driver seats: The effects of automated vehicle characteristics on cyclists’ decision‐making

“…[41]), or real cars (e.g. Forke et al [42]). However, these methods are not useful for tightly controlled evaluations using large sample sizes.…”

External human–machine interfaces: Gimmick or necessity?

“…There is a limited but growing number of eHMI studies conducted with real vehicles, but typically in simple settings such as parking lots (Ahn et al, 2021;Chen et al, 2020;Hensch et al, 2020;Liu et al, 2021), indoor environments (Burns et al, 2019;Reschke et al, 2018), test tracks (Faas et al, 2021;Fuest et al, 2020;Horn et al, 2021), or roads with otherwise restricted access (Barendse, 2019;Dey et al, 2021a;Habibovic et al, 2018;Joisten et al, 2019;Morales Alvarez et al, 2019;Mührmann, 2019;Papakostopoulos et al, 2021;Zadeh Darrehshourian, 2021). Research in real traffic is still relatively rare (Cefkin et al, 2019;Forke et al, 2021;Merat et al, 2018;Mirnig et al, 2021;Monzel et al, 2021), and some evidence concurs that eHMIs will have to compete with other visual cues in the environment. In particular, Cefkin et al (2019) found that, in real traffic, which can be busy and requires distributed visual attention, pedestrians often did not even notice the eHMI on the car.…”

Consumer Acceptance in Measuring Greece’s Readiness for Transport Automation

“…Such work is mostly related to improving the user experience along with minimizing potential side-effects which would discourage the choice of AV or create a negative impression of the users towards their introduction. In this sense, different research initiatives have focused on presenting alternative Human Machine Interface (HMI) to facilitate user experience and interaction with AVs, either inside [11][12][13] or outside [14][15][16] the vehicle (addressing conspicuity and traffic interaction issues). Moreover, issues related to the network capabilities and its optimal response to the needs generated by AV operation are another topic of research interest [17], tackling, among others, with the optimization of cloud networks for addressing AV performance and IoT needs in general.…”