A method of and a navigation device for time-dependent route planning

Claimed is a system and a computer-implemented method of planning a route to a destination, based upon a fixed, predefined time-independent cost associated with each different route segment in a map database; a historical time-dependent cost, associated with at least some of the route segments in the map database; and updated time-dependent cost for some of the route segments for a current or a future time based on an identification of currently congested route segments by a traffic monitoring system, as well as a computer-implemented method processing traffic monitoring data to generate a database of historical time-dependent traffic speeds or transit times for some route segments in a map database; to identify currently congested route segments; and to predict a traffic speed or transit time for a future time for at least one currently congested route segment.