Allusion 2: External Communication for SAE L4 Vehicles


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Safe-D University Transportation Center


With SAE Level 4 and above (L4+) Automated Driving Systems (ADSs) being integrated on roadways, stakeholders worldwide are developing external communication systems for other road users to communicate effectively. Most research on SAE L4+ ADS external communication has used simulators or virtual reality platforms to assess driver/road user knowledge, opinions, and attitudes via survey metrics evaluating a single L4 vehicle. However, it is vital to understand perception of external communication in real-world conditions and with multiple SAE L4+ ADSs present. This research explored how the presence of multiple SAE L4+ ADSs with external communication displays affected participants’ crossing decisions. A within-subject design assessed participants’ understanding of SAE L4+ ADS intentions. Results indicated that the presence and condition of external human-machine interfaces (eHMIs) did not influence willingness to cross. It was difficult for participants to focus on the eHMI when multiple vehicles competed for their attention. Participants typically focused on the vehicle that was nearest and most detrimental to their crossing path. Scenario type caused participants to make more cautious crossing decisions but did not influence willingness to cross. This study implies that eHMI with two patterns may still require simplification for pedestrians to interpret in a complicated traffic environment.



SAE Level 4+ automated vehicles, external communication, SAE L4+ AV, pedestrian, vulnerable road users, VRU, driving scenario