Patent ID: 7171306

Claim:
A route searching system comprising: a road map database for storing a road map data, the road map data including (i) node data that indicates nodes that correspond to predetermined kinds of points on a road including at least an intersection, and (ii) link data that indicates a link that corresponds to a road section that connects the predetermined kinds of points on a road corresponding to the nodes; and a searching device for calculating link costs as for individual links that correspond to individual road sections that consist of individual route options from a first point to a second point, on the basis of said road map database, and thereby searching one of the individual route options whose total link cost is the lowest, as an optimal route, from among a plurality of links that correspond to all the road sections of the individual route options, wherein said searching device increases or decreases the link cost of a link corresponding to a road section that requires a difficult turn on the individual route options, the difficult turn being the right turn or the left turn one of which is more difficult than the other in accordance with a traffic rule, and connecting to a node that corresponds to the intersection, in at least two cases depending on difficulty of the difficult turn at the intersection.