The objective of this pilot study was to investigate how far dimensional constraints (vision requirements, head clearance) influence postures of car drivers. For that purpose the preferred sitting postures of 9 subjects were recorded twice. Furthermore the drivers were interviewed regarding their perceived comfort. The data show that limited vision conditions, head clearance and maximum adjustment travels influence the subjective rating, joint angles, eye and head position. It can be concluded that these factors should be considered in posture studies and included in posture models intended for posture prediction what has not been done yet. In further investigations, results so far found in this study have to be verified with larger samples and in other packages or cars under dynamic test conditions.