Map display system, method, and program

A map display system comprising: a map information acquiring unit, a congestion level acquiring unit, a route line display determining unit that determines whether a route line (P), representing a planned travel route, is displayed superimposed on a road line (R) representing a road section within the map, and a display controlling unit. If the route line is displayed superimposed on a road line: . a congestion line (J) representing the congestion level is displayed offset by a first off-set distance from the road line, determined so that the route line is not overlapped with the congestion line. If the route line is not displayed superimposed on a road line: . the congestion line is displayed offset by a second off-set distance from the road line, determined so that the road line is not overlapped with the congestion line. The invention also encompasses a corresponding map display method and program.