New driver assistance systems can increase safety in today’s traffic. However, if the mental model and knowledge of a system is incorrect or incomplete, these systems cannot unfold their full positive potential. To get an insight on mental models, many different measurement approaches have been used so far. However, some of them need to interrupt the driving task or could possibly give clues to the actual functioning of the system by asking about the features. Aim of this study is to gain an impression of the applicability of a subjective workload scale supporting the measurement of mental model development. This could provide an opportunity for an additional simple method that can be used in the driving context. Therefore, we looked at the connection between subjective cognitive workload and the development of the mental model about a driver assistance system in a driving simulator setting. Participants were differently instructed in the system functionalities. They experienced the system including lateral and longitudinal support in different urban and highway situations driving in a dynamic simulator. Within the two environments several scenarios were presented. Results show a development of subjective mental workload depending on the experienced situation. Findings regarding a possible connection with mental model development were heterogeneous.