In order to alleviate congestion in a large parking lot, it is important to set the layout of parking spaces and the direction of aisles appropriately. Our group has started the development of a usage analysis method as the first step in research on parking lot layout optimization using computer simulation. In this study, we propose a vehicle detection method based on segmentation and position estimation to analyze the parking lot usage situation, and conduct experiments using videos taken in parking lots to examine the effectiveness of the proposed method.