Investigating the Perception of Pedestrians in Car 2 Human Communication: A Case Study Using Different Symbols and Dynamics to Communicate Via an Angular Restricted eHMI and Road Projections 2022-01-0800

It has been shown that additional light signals are beneficial in the car 2 human communication. This study addresses detection, discomfort, brightness, recognition of intention and the perception of safety, of different symbols and dynamics used for communication. Splitted in two parts, the first use case is a lane crossing situation, where the car gives instructions to the pedestrian via an angular restricted external Human Machine Interface (eHMI) in the driver’s window. Results show that a symbol which blinks first and is then statically shown leads to fast and best detection. The intention of a red stop hand and green pedestrian is clearly understood. A combination of a near road-projection and the eHMI leads to confusion. An angle of 55° to 25° has been proven to be sufficient for displaying the information. In the second use case a cyclist is approaching the automated vehicle (AV) from behind and passes on a bicycle path. A white arrow pointing to the right and a white straight arrow were supposed to show the AV’s intention, but results show that it was not clear whether the AV is giving instructions or projecting its next move. Also, there was no difference between a blinking animation and a sequential animation in terms of the cyclist's feeling of being recognized, detected and the understanding of the intention. There was a tendency that a sequential animation is more comfortable and leads to enhanced feeling of safety. The results show that the dynamic has a minor influence on the understanding of intention. A combination of the symbols with different colors could be used to indicate whether the AV is giving instructions or projecting its behavior.