Navigation device

A navigation device mounted on a vehicle, comprising:

• a map data storing means for storing data on a road map;
• a current position detecting means for detecting the current position of the vehicle and for outputting data of the current position of the vehicle in order to display a current position mark;
• a traffic information receiving means for receiving traffic information including traffic-jam information;
• a display means for displaying a road map of an area in which the vehicle is travelling based on said data on the road map, and displaying said current position mark based on said data of the current position of the vehicle;
• and
• a display form controlling means for determining roads in a traffic-jam based on said traffic information received in said receiving means, for displaying a traffic-jam indicating symbol along a road in a traffic jam on the road map displayed on said display means, and for changing display forms of either roads or traffic-jam indicating symbols on the road map on-screen when said display form controlling means determines from the traffic information received that a number of links each of which are respectively connecting two nodes such as intersections and includes a congested road section is equal to or more than a predetermined number.