Head-up displays present driving-related information close to the road scene. The content is readily accessible, but potentially clutters the driver’s view and occludes important parts. This can lead to distraction and negatively influence driving performance. Superimposing display content only on demand – triggered by the driver whenever needed – might provide a good tradeoff between the accessibility of relevant information and the distraction caused by its display. In this paper we present a driving simulator study that investigated the influence of the self-triggered superimposition on workload, distraction and performance. In particular, we compared a gaze-based and a manually triggered superimposition with the permanent display of information and a baseline (speedometer only). We presented four pieces of information with different relevance and update frequency to the driver. We found an increased workload and distraction for the gaze- and manually triggered HUDs as well as an impact on user experience. Participants preferred to have the HUD displayed permanently and with only little content.