Generating Concise and Robust Driving Directions

We consider the problem of generating concise and robust driving directions that avoid overly detailed turn-by-turn instructions as long as one is not too close to the final destination. Our approach is based on a deliberate selection of cities as landmarks that are likely to appear on road signs along the route. For a route from Stuttgart to Flensburg, the route description could read "Go towards Frankfurt, then Kassel, then Hanover, then Hamburg". Apart from being more compact, such driving directions are also more robust against wrong turns taken. While an implementation based on Dijkstra's algorithm takes on the order of several seconds to generate such driving directions, a careful instrumentation of speed-up techniques reduces this to fractions of a second required, e.g., for a web service.