A navigation system may estimate a cruising range of a vehicle by performing a road network search. Digital map data that includes a set of road segments, where each road segment in the set can be associated with a hierarchy class and an elevation, may be retrieved. A road segment-specific weighting factor can be calculated for the road segments. The weighting factor can be calculated dependent on a distance of the specific road segment to a current location of the vehicle and on the elevation of the specific road segment. The road segments are selectively discarded by the navigation system based on the weighting factor and the associated hierarchy class to create a selected set of road segments. The road network search expands route links for the selected set of road segments based on an associated estimated energy consumption of the vehicle travelling along the route links.