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Context-Based Interface Prototyping: Understanding the Effect of Prototype Representation on User Feedback

Marius Hoggenmueller, Martin Tomitsch, Luke Hespanhol, Tram Thi Minh Tran, Stewart Worrall, Eduardo Nebot

TL;DR

This paper tackles how the choice of prototype representation affects user feedback on context-based interfaces for autonomous vehicles. It conducts a between-subject mixed-methods study comparing real-world VR, computer-generated VR, and real-world video representations of an eHMI in a shared urban environment, measuring sense of presence, trust, and user experience. Findings show VR representations enhance presence and ecological validity, while trust in the AV is influenced by realism and environmental context rather than representation alone; qualitative data reveal distinct experiential focuses across representations. The study provides actionable guidelines for selecting simulation platforms, structuring scenes, and designing CG-VR prototypes to optimize feedback quality and ecological validity in prototyping context-based interfaces for urban autonomous mobility.

Abstract

The rise of autonomous systems in cities, such as automated vehicles (AVs), requires new approaches for prototyping and evaluating how people interact with those systems through context-based user interfaces, such as external human-machine interfaces (eHMIs). In this paper, we present a comparative study of three prototype representations (real-world VR, computer-generated VR, real-world video) of an eHMI in a mixed-methods study with 42 participants. Quantitative results show that while the real-world VR representation results in higher sense of presence, no significant differences in user experience and trust towards the AV itself were found. However, interview data shows that participants focused on different experiential and perceptual aspects in each of the prototype representations. These differences are linked to spatial awareness and perceived realism of the AV behaviour and its context, affecting in turn how participants assess trust and the eHMI. The paper offers guidelines for prototyping and evaluating context-based interfaces through simulations.

Context-Based Interface Prototyping: Understanding the Effect of Prototype Representation on User Feedback

TL;DR

This paper tackles how the choice of prototype representation affects user feedback on context-based interfaces for autonomous vehicles. It conducts a between-subject mixed-methods study comparing real-world VR, computer-generated VR, and real-world video representations of an eHMI in a shared urban environment, measuring sense of presence, trust, and user experience. Findings show VR representations enhance presence and ecological validity, while trust in the AV is influenced by realism and environmental context rather than representation alone; qualitative data reveal distinct experiential focuses across representations. The study provides actionable guidelines for selecting simulation platforms, structuring scenes, and designing CG-VR prototypes to optimize feedback quality and ecological validity in prototyping context-based interfaces for urban autonomous mobility.

Abstract

The rise of autonomous systems in cities, such as automated vehicles (AVs), requires new approaches for prototyping and evaluating how people interact with those systems through context-based user interfaces, such as external human-machine interfaces (eHMIs). In this paper, we present a comparative study of three prototype representations (real-world VR, computer-generated VR, real-world video) of an eHMI in a mixed-methods study with 42 participants. Quantitative results show that while the real-world VR representation results in higher sense of presence, no significant differences in user experience and trust towards the AV itself were found. However, interview data shows that participants focused on different experiential and perceptual aspects in each of the prototype representations. These differences are linked to spatial awareness and perceived realism of the AV behaviour and its context, affecting in turn how participants assess trust and the eHMI. The paper offers guidelines for prototyping and evaluating context-based interfaces through simulations.
Paper Structure (41 sections, 4 figures, 3 tables)

This paper contains 41 sections, 4 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Related Work
  3. External Human-Machine Interfaces
  4. Prototyping and Simulation
  5. Simulation Platforms
  6. Evaluation Study
  7. Study Design
  8. Prototype Representations
  9. RW-VR
  10. CG-VR
  11. RW-Video
  12. Participants
  13. Study Procedure
  14. Data Collection
  15. Questionnaires
  16. ...and 26 more sections

Figures (4)

  • Figure 1: Recording setup for the immersive 360-degree real-world video prototype representation.
  • Figure 2: Scenes (S1-3) and trajectories for the 360-degree video recording and the light patterns (L1-L4) used in the AV's eHMI for the various simulated interactions. Colours in the trajectories represent the colour encoding, which has been used for riders to identify their vehicle (i.e. blue for Actor 2, purple for the user experiencing the prototype in VR).
  • Figure 3: Frames from the RW-VR and CG-VR simulations and the RW-Video setup used as conditions in the study (top). Study procedure showing the way participants experienced each of the prototype representations and the data collected (bottom).
  • Figure 4: UX assessment of the eHMI across the three representations, based on the UEQ questionnaire Laugwitz2008.