Current in-car navigation systems provide only a limited level of adaption to the driver and driving conditions. The driver's actual information need while interacting with the navigation interface is not taken into account. This paper aims at investigating the impact of situational features on the drivers' support need as well as proposing modes of adaptation for situation-aware navigation support. Therefore, three studies were conducted. It became evident that the driver's need for more or less navigation support depends on the complex interplay of different characteristics of the driver, the vehicle, and the driving environment. Based on our findings, a set of driving situation related adaption rules for a more user centered navigation support is proposed.