1. A route planning method for constructing a route connecting a given origin location and a given destination location from a hierarchical map database having a plurality of layers each layer representing a different level of detail, the method comprising the steps of: providing a list of road segments extracted from an initial planning layer of the hierarchical map database, wherein each of the road segments in the list of road segments are connected to the given origin location; and selecting an alternative planning layer dependent on exceeding a predetermined heading criteria measured between a heading associated with one of the road segments in the list of road segments and a heading associated with the given destination location.