In this article, we aim to contribute to the emerging field of risk-work studies by examining the relationship between risk rationality and risk practices in nurses’ conversations with Obstructive Sleep Apnoea patients about traffic risks. Legislation in Sweden towards traffic risk involves clinicians making risk assessment of patients prone to falling asleep while driving. In contrast to an overall care rationale, this means that the health of the patient is not the only risk object in treatment consultations. However, guidelines on how to implement legislation are missing. To examine the practical reality of nurses’ traffic-risk work, we draw on an analysis of data from a Swedish study in 2015. This study included qualitative interviews with specialist nurses and video-recorded interactions between nurses and Obstructive Sleep Apnoea patients. We found that a lack of clarity in traffic-risk guidelines on how risk should be addressed was evident in both interview accounts and in observed practice. While nurses primarily accounted for risk work as treatment-relevant education, they practised risk work as interrogation. Patients also treated nurses’ inquiries as assessment – not education – by responding defensively. We conclude that while confusing risk work and treatment enables clinicians to treat patients as competent actors, it obscures the controlling aspects of traffic-risk questions for individual patients and downplays the implications of drowsy driving for general traffic safety.