Ranking Crossing Scenario Complexity for eHMIs Testing: A Virtual Reality Study

Abstract

External human–machine interfaces (eHMIs) have the potential to benefit AV–pedestrian interactions. The majority of studies investigating eHMIs have used relatively simple traffic environments, i.e., a single pedestrian crossing in front of a single eHMI on a one-lane straight road. While this approach has proved to be efficient in providing an initial understanding of how pedestrians respond to eHMIs, it over-simplifies interactions which will be substantially more complex in real-life circumstances. A process is illustrated in a small-scale study (N = 10) to rank different crossing scenarios by level of complexity. Traffic scenarios were first developed for varying traffic density, visual complexity of the road scene, road geometry, weather and visibility conditions, and presence of distractions. These factors have been previously shown to increase difficulty and riskiness of the crossing task. The scenarios were then tested in a motion-based, virtual reality environment. Pedestrians’ perceived workload and objective crossing behaviour were measured as indirect indicators of the level of complexity of the crossing scenario. Sense of presence and simulator sickness were also recorded as a measure of the ecological validity of the virtual environment. The results indicated that some crossing scenarios were more taxing for pedestrians than others, such as those with road geometries where traffic approached from multiple directions. Further, the presence scores showed that the virtual environments experienced were found to be realistic. This paper concludes by proposing a “complex” environment to test eHMIs under more challenging crossing circumstances.

Does another pedestrian matter? A Virtual Reality study on the interaction between multiple pedestrians and autonomous vehicles in shared space

“…Our interpretation is that when the far-away participant experienced the second block (i.e., two-pedestrian scenarios) after the first block (single-pedestrian scenarios), the sudden appearance of another person in the environment distracted and caught their attention, leading to longer decision time. Studies suggest that distracted pedestrians tend to initiate late road crossing [7], this is further confirmed by the longer gazing time toward another pedestrian. This finding is in line with [38], which similarly observed that participants farther from the AV chose narrower time margins to enter the road.…”

“…The questionnaire included seven parts, namely (1) participant's information, (2) the face validity questionnaire, (3) the Simulator Sickness Questionnaire, (4) the Presence Questionnaire, (5) the Trust in AVs questionnaire, (6) the Perceived behavioral control and risk questionnaire, and (7) the System Usability Scale questionnaire. The personal information part included participants' characteristics such as gender, age, achieved highest education level, familiarity with the Marineterrein area, familiarity with computer gaming, familiarity with VR, familiarity with the concept of AVs, and experience regarding interaction with AVs.…”

“…Compared to more traditional unsignalized traffic situations, a few studies investigated pedestrian-AV interaction in unmarked crossings, junctions, and intersections [5]. Studies indicate that pedestrian road crossing decision is related to the intricacy of traffic situations [7]. While pedestrian-AV interaction in various types of unsignalized traffic situations has been studied, their interaction in shared spaces has been rarely studied.…”

“…To summarize, most of the above-mentioned studies investigated one-on-one pedestrian-AV interaction in relatively simple traffic scenarios, while shared spaces-a type of traffic situation characterized by increased uncertainty and versatility-have received less attention. Literature suggests that when the complexity of traffic situations increases, pedestrians perceive a higher risk and therefore behave more cautiously [7]. Moreover, some studies suggest that the scalability and suitability of eHMI need to be examined for more complex traffic scenarios [2,39].…”

External human–machine interfaces: Gimmick or necessity?

“…The literature is replete with examples of confusing eHMI messages, such as the text GO (Eisma et al, 2021), arrows (Kunst et al, 2022;Zang et al, in press), and a red lamp (Bazilinskyy et al, 2020) being misunderstood regarding whether the message represents an instruction for the pedestrian or a representation of the AV's intent. Also, some light-based eHMIs have been misinterpreted as sensors instead of communication devices (Bazilinskyy et al, 2019;Fratini et al, 2021;Shutko et al, 2018).…”