To minimize the mental workload for the driver and to keep the increasing amount of information easily accessible, sophisticated display and interaction techniques are essential. This contribution focuses on a user-centered analysis for an authoritative grading of head-up displays (HUDs) in cars. Two studies delivered the evaluation data. In a field test, the potential and the usability of the HUD were analyzed. For special driving situations the according display needs and requirements of the users have been identified and compared with in-car displays, so-called head-down displays (HDD). As major result, a high acceptance of the HUD by the driver and a good performance compared to other in-car displays had been reached.