Assessment of Bicycle–Vehicle Conflicts in Digital-Twin Environment with Various Levels of Connectivity

Intersections present considerable safety risks for bicyclists, where road space shared with vehicles frequently triggers conflicts. Although connected technologies promise safety benefits, they may trigger additional stress and adverse behavioral changes, making it important to investigate their impact on bicyclist–vehicle conflicts. This study introduces a novel experimental framework that integrates a high-fidelity digital twin of a one-way signalized arterial (Delaware Avenue in Newark, DE, United States) with a dual human-in-the-loop simulator, allowing real-time interaction between a human-driven vehicle and a human-operated bicycle. The digital twin combines CARLA, used for immersive participant simulation, and PTV Vissim, which replicates realistic background traffic conditions. The first step was to identify potential conflict situations by considering traditional surrogate safety measures and validating them as real conflicts with self-reported feedback and physiological stress responses. Results confirmed that the experimental setup produced events meeting both kinematic and stress-based conflict criteria. The second stage focused on how connected technologies influence user experience, specifically whether collision warning information evokes additional stress, given its novelty and limited adoption in real-world contexts. Finally, we examined behavioral changes by analyzing approach and postconflict speeds, revealing how connectivity affects speed choices in conflicting situations, with drivers increasing approach speeds and bicyclists becoming more cautious. This research demonstrates the value of combining digital twins, dual human-in-the-loop simulators, and physiological sensing for studying connected safety technologies. The findings provide new insights into how connectivity influences user stress and behavior, helping the design and evaluation of future connected multimodal traffic systems.