Objective: The aim of this study was to investigate the effect of autonomous-vehicle-to-pedestrian (AV2P) communication through augmented reality (AR) interfaces on the road crossing behaviour of pedestrians, and research whether subjective results from a previous Cave Automatic Virtual Environment (CAVE) study replicated in a real world AR experiment.
Background: Previous studies investigating the effects of AV2P communication have mostly been conducted through virtual reality (VR) providing researchers with safe experimentation methods and high experimental control, but also resulting in a common limitation: the lack of ecological validity and realism, thereby affecting participants’ behaviour and causing distractions. This study therefore introduces AR experiments that have been conducted in a real world environment to increase ecological validity.
Methods: An AR experiment was conducted in which 28 participants were situated in the real world with the objective to cross the road. The virtual vehicle, that was projected through a Varjo XR-3 head mounted display, approached from the right at a speed of 30 km/h while 4 interfaces (2x world-locked, head-locked, and vehicle-locked) appeared to communicate the vehicle’s intention towards the participants, in addition to a no-interface baseline. Participants were tasked with indicating when they were willing to cross through the push of a remote button from which their Willingness to cross and Decision certainty could be derived. Subjective data was collected after the trials and after the experiment through interviews and a questionnaire respectively.
Results: Results suggest a positive effect of the AV2P interfaces on the Willingness to cross and Decision certainty, although statistically not significant. In other words, Willingness to cross increases when the vehicle indicates that it will yield, and decreases when the vehicle communicates that it will not yield. Decision certainty also increases when an interface is present compared to the no-interface baseline. Moreover, participants indicated using the interfaces as a tool to validate their own decisions. Compared to the CAVE study, subjective intuitiveness ratings replicate in terms of observing higher intuitiveness of the interfaces than the no-interface baseline. However, the intuitiveness ratings were higher in the CAVE study than the real world AR experiment. Furthermore, the order of the top 3 most preferred interfaces ranking is in the opposite order. Both differences suggest that the increased ecological validity of the real world AR experiment introduces new insights into participants’ perception of interfaces. The Van der Laan acceptance scale shows that participants believe interfaces to be useful and satisfying overall.
Conclusion: The experiments suggest that AV2P interfaces have a positive effect on the crossing behaviour of pedestrians. Furthermore, participants indicate using the interfaces as a tool to validate their own decision, which increases confidence in their decisions. Although results partially replicate a previous virtual environment study, there are differences that suggest that real world AR experiments provide valuable insights into participants’ perception of interfaces in a more realistic experiment.