Abstract: Systems, methods, and programs for navigation guide to a destination along a searched route and receive road information and traffic information including traffic congestion information. If according to the received traffic congestion information, traffic congestion is detected on the guidance route, the systems, methods, and programs search a detour route to avoid such congestion. The systems, methods, and programs guide to a destination along the detour route. If traffic congestion which was previously avoided by the detour route is determined to have been eased, the systems, methods, and programs search for a new route and switches guidance from the detour route to the new route.