The development of cyber-physical systems such as automated driving systems calls for proper engineering methods to ensure that the risk of causing harm to people is minimized. The increasing complexity of environment in which CPS have to function and the complexity of their interaction is becoming a potential source of risk. This becomes evident in recent standards such as ISO 21448, which specify respective requirements on considering the environment in the engineering process. Developing concepts and methods that effectively address these requirements is subject of ongoing research. This paper contributes to the research by putting ontologies into focus. It argues that making an ontology of the operational domain an explicit design artifact can greatly support the engineering process. To this end, the paper discusses its use in several key phases of an ISO 26262-compliant engineering process along a small running example, and looks into state of the art related to ontologies.