Car navigation system, corresponding navigation method and storage medium

The invention allows to accurately determine the vehicle estimated position on a multilayer road even under various situations. A car-navigation system is provided for determining an estimated position of a vehicle comprising a first judgment means for judging expressway as a first road predominant as estimated position, a second judgment means for judging ordinary road as a second road predominant as estimated position, and control means for determining the vehicle estimated position based on the judgment results of the first and second judgment means.