In domestic roundabouts, various safety measures such as structural improvements and signage have been implemented, but they often prioritize the perspective of car users. However, there are few cases where roundabouts are installed in areas with high bicycle traffic. As a result, many examples exist where measures such as chevron pavement markings and signage are implemented to guide bicycle travel positions and prevent conflicts with cars. Additionally, analyzing the effectiveness of these measures is challenging due to construction constraints. Therefore, the purpose of this study is to investigate and analyze the actual bicycle usage patterns at roundabouts without pavement markings or similar interventions in order to reveal the characteristics of bicycle usage based on differences in bicycle travel positions. Furthermore, the objective is to contribute to the consideration of bicycle safety measures in future roundabout designs.