Case Study—This case study presents ethnographic work in the midst of two fields of technological innovation: automated vehicles (AV) and virtual reality (VR). It showcases the work of three MSc. Techno-Anthropology students and their collaboration with the EU H2020 project ‘interACT’, sharing the goal to develop external human-machine interfaces (e-HMI) for AVs to cooperate with human road users in urban traffic in the future. The authors reflect on their collaboration with human factor researchers, data scientists, engineers, experimental researchers, VR-developers and HMI-designers, and on experienced challenges between the paradigms of qualitative and quantitative research. Despite the immense value of ethnography and other disciplines to collectively create holistic representations of reality, this case study reveals several tensions and struggles to align multi-disciplinary worldviews. Results show the value of including ethnographers: 1) in the design and piloting of a digital observation app for the creation of large datasets; 2) in the analysis of large amounts of data; 3) in finding the potential of and designing e-HMI concepts; 4) in the representation of real-world context and complexity in VR; 5) in the evaluation of e-HMI prototypes in VR; and finally 6) in critically reflecting on the construction of evidence from multiple disciplines, including ethnography itself.