Future automated vehicles may be equipped with external human-machine interfaces (eHMIs) capable of signaling to pedestrians whether or not they can cross the road. There is currently no consensus on the correct colors for eHMIs. Industry and academia have already proposed a variety of eHMI colors, including red and green, as well as colors that are said to be neutral, such as cyan. A confusion that can arise with red and green is whether the color refers to the pedestrian (egocentric perspective) or the automated vehicle (allocentric perspective). We conducted two crowdsourcing experiments (N = 2000 each) with images depicting an automated vehicle equipped with an eHMI in the form of a rectangular display on the front bumper. The eHMI had one out of 729 colors from the RGB spectrum. In Experiment 1, participants rated the intuitiveness of a random subset of 100 of these eHMIs for signaling 'please cross the road', and in Experiment 2 for 'please do NOT cross the road'. The results showed that for 'please cross', colors close to pure green were considered the most intuitive. For 'please do NOT cross', colors close to pure red were rated as the most intuitive, but with high standard deviations among participants. In addition, some participants rated green colors as intuitive for 'please do NOT cross'. Results were consistent for men and women and for colorblind and non-colorblind persons. It is concluded that eHMIs should be green if the eHMI is intended to signal 'please cross', but green and red should be avoided if the eHMI is intended to signal 'please do NOT cross'. Various neutral colors can be used for that purpose, including cyan, yellow, and purple.
|Title of host publication||Proceedings of the IEEE International Conference on Systems, Man, and Cybernetics, SMC 2020|
|Place of Publication||Piscataway, NJ, USA|
|Publication status||Published - 2020|
|Event||2020 IEEE International Conference on Systems, Man, and Cybernetics, SMC 2020 - Toronto, Canada|
Duration: 11 Oct 2020 → 14 Oct 2020
|Conference||2020 IEEE International Conference on Systems, Man, and Cybernetics, SMC 2020|
|Period||11/10/20 → 14/10/20|
Bibliographical noteGreen Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care
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 driving
- external humanmachine interface
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Supplementary data for the paper 'External Human-Machine Interfaces: Which of 729 Colors Is Best for Signaling ‘Please (Do not) Cross’?'