Online map programs such as MapQuest or Google Maps have made it easier for many people to plan road trips. But to handle large numbers of requests for driving directions, such systems often don't search the entire range of possible routes, says Dominik Schultes, a computer scientist at the University of Karlsruhe in Germany. For example, the systems may overlook shorter routes for the sake of following major highways, he says.
Schultes and his collaborators have now invented an algorithm that can efficiently deliver the best directions with mathematical certainty—save for traffic jams—the researchers say.
Schultes says that the new algorithm exploits a common-sense observation no other algorithm had used before: Each route into or out of a city typically passes through one of a handful of major intersections.