Understanding how human drivers interact in dynamic traffic situations is a crucial step toward the safe and seamless integration of automated vehicles (AVs) into everyday traffic. A common setting for these interactions is the four way single-lane roundabout. Here, drivers must make quick decisions about who yields and who proceeds, based not just on traffic rules but also on subtle cues and shared expectations. These decisions rely heavily on gap acceptance, where each driver evaluates whether there is enough space and time to enter the roundabout safely. It often depends on mutual negotiation and split-second judgments, shaped by visual contact and behavioral feedback.
While earlier studies have explored driver gaze behavior in controlled environments, little is known about how gaze correlates with decision-making in continuous and mutual encounters, especially at roundabouts. This study fills that gap by studying human-human interactions during roundabout entry in a novel experimental setup. Using a coupled virtual reality driving simulator, two participants navigated a single-lane roundabout under varying approach speeds and distances. Eye-tracking was used to measure where and how long each driver fixated at the other vehicle. Control input data captured how drivers reacted in the seconds following these gaze events.
The results show that both entry distance and speed had a strong influence on who proceeded first. Drivers who started closer to the roundabout or moved faster were more likely to take priority. Drivers positioned closer to the conflict zone looked at the other vehicle for longer durations, indicating stronger visual engagement. Furthermore, drivers often responded with throttle or brake inputs shortly after looking at the other vehicle, especially when distance to the roundabout was small.
This study offers insight into how gaze behavior, positioning and control decisions shape mutual negotiation at roundabouts. These findings move beyond the idea of gap acceptance as a one-sided decision and highlight the importance of real-time interaction.