Survey on eHMI concepts: The effect of text, color, and perspective

Pavlo Bazilinskyy*, Dimitra Dodou, Joost de Winter

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

84 Citations (Scopus)
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The automotive industry has presented a variety of external human-machine interfaces (eHMIs) for automated vehicles (AVs). However, there appears to be no consensus on which types of eHMIs are clear to vulnerable road users. Here, we present the results of two large crowdsourcing surveys on this topic. In the first survey, we asked respondents about the clarity of 28 images, videos, and patent drawings of eHMI concepts presented by the automotive industry. Results showed that textual eHMIs were generally regarded as the clearest. Among the non-textual eHMIs, a projected zebra crossing was regarded as clear, whereas light-based eHMIs were seen as relatively unclear. A considerable proportion of the respondents mistook non-textual eHMIs for a sensor. In the second survey, we examined the effect of perspective of the textual message (egocentric from the pedestrian's point of view: ‘Walk’, ‘Don't walk’ vs. allocentric: ‘Will stop’, ‘Won't stop’) and color (green, red, white) on whether respondents felt safe to cross in front of the AV. The results showed that textual eHMIs were more persuasive than color-only eHMIs, which is in line with the results from the first survey. The eHMI that received the highest percentage of ‘Yes’ responses was the message ‘Walk’ in green font, which points towards an egocentric perspective taken by the pedestrian. We conclude that textual egocentric eHMIs are regarded as clearest, which poses a dilemma because textual instructions are associated with practical issues of liability, legibility, and technical feasibility.

Original languageEnglish
Pages (from-to)175-194
JournalTransportation Research Part F: Traffic Psychology and Behaviour
Publication statusPublished - 2019

Bibliographical note

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project

Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.


  • Automated vehicles
  • Crowdsourcing
  • External Human-Machine Interface (eHMI)
  • Online surveys

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