Shortest path calculation in large road networks

One of the basic problems in transportation planning systems is the calculation of the fastest route between two points in a road network. General shortest path algorithms, which examine a large part of the whole graph for each shortest path, are very slow if the road network is large. Since the road network does not change very often it is possible to calculate auxiliary information in a preprocessing step. I will present a preprocessing algorithm which requires linear storage. It is substantially faster than the general algorithms without preprocessing.