Robust, Almost Constant Time Shortest-Path Queries in Road Networks

When you drive to somewhere ‘far away’, you will leave your current location via one of only a few ‘important’ traffic junctions. Recently, other research groups and we have largely independently developed this informal observation into transit node routing, a technique for reducing quickest-path queries in road networks to a small number of table lookups. The contribution of our paper is twofold. First, we present a generic framework for transit node routing that allows almost constant time routing for both global and local queries. Second, we develop a highly tuned implementation using highway hierarchies. For the road maps of Western Europe and the United States, our best query times improve over the best previously published figures by two orders of magnitude. This is more than one million times faster than the best known algorithm for general networks. We also explain how to compute complete descriptions of shortest paths (and not only their lengths) very efficiently.