Embodiments of the present invention provide a computer implemented method of route comparison, comprising receiving data indicative of first and second routes between a start location and a destination location wherein the first and second routes are generated using digital map data, determining nodes of the first and second routes having a minimum coupling distance, wherein the minimum coupling distance is determined based upon nodes of the first and second routes constrained to within a predetermined distance of a current node of each route, and determining a similarity index for the first and second routes based upon the minimum coupling distance and a threshold data coupling distance.