A major challenge for autonomous vehicles (AVs) today is driving in a complex urban environment where various traffic participants, infrastructures, and events are mixed. A growing body of research is studying the interaction between AVs and human road users (HRUs) to mitigate this challenge. Although traffic is complicated, research has focused on limited situations, such as pedestrian crossings. This study aims to explore scenarios that have a high possibility of causing problems in mixed traffic situations. We devised a design workshop method using miniatures and small cameras, thus allowing participants to experience scenarios from the HRU perspective and easily creating new road situations to uncover various problems. By analyzing 133 scenarios found through the workshop, we defined five factors and 51 elements of AV–HRU problem scenarios. Through qualitative analysis of the factors found through experiments and comparison with existing studies, we identified research gaps and discussed future design challenges.