Automated Shuttle buses (ASB) are considered an essential and sustainable direction for the future application of autonomous driving technology in public transportation. As the driver’s role gradually decreases and disappears, the Human–Machine Interface (HMI) for information exchange and communication between users and ASB takes a more prominent role and progressively becomes a hotspot in research. However, the unpredictability and complexity of autonomous driving, an exceptionally fast-growing technology, have hindered its future study. This work first reviewed related literature in three categories: internal, external, and station of the ASB. Secondly, the importance of systemic and speculative design is affirmed by exploring existing HMI designs for ASB. Thirdly, the concepts for ASB resulting from three parallel workshops were analyzed. Finally, online questionnaires and interviews completed the critical reflection and discussion. The results show that the introduction of tools and methods related to systemic and speculative design into the design process of the HMI for ASB may help designers to think critically about the future uncertainty of ASB and to deal with the complexity of the system.