Don't drive me my way - Subjective perception of autonomous braking trajectories for pedestrian crossings

Autonomous vehicles will encounter all the traffic situations that current drivers are confronted with. These vehicles are expected to handle the situations at least as good as human drivers or even better. This "better" can be split up in various ways and address different facets of traffic: safety, efficiency, and cooperativity to name a few. The driving simulator study at hand investigated the effect of different braking trajectories of a fully autonomous vehicle (SAE Level 5) approaching a zebra crossing. Participants had to rate two aspects: (1) the perceived cooperativity and (2) the perceived criticality of the programmed braking trajectories, in addition to a replay of their own, manual approach, in a dynamic driving simulator. The results show significant differences between the approaches in terms of how critical and cooperative they were perceived. Remarkably, the participants' individual driving style was, on average, not the safest or most cooperative one. Participants favourized an approach with an early brake onset with gradually increasing and subsequent decreasing brake intensity (bell-shaped curve) until full stop in front of the pedestrian crossing.