Chapter

Algorithms – ESA 2010

Volume 6346 of the series Lecture Notes in Computer Science pp 290-301

Fast Routing in Very Large Public Transportation Networks Using Transfer Patterns

  • Hannah BastAffiliated withAlbert-Ludwigs-Universität FreiburgGoogle
  • , Erik CarlssonAffiliated withGoogle
  • , Arno EigenwilligAffiliated withGoogle
  • , Robert GeisbergerAffiliated withKarlsruhe Institute of Technology (KIT)Google
  • , Chris HarrelsonAffiliated withGoogle
  • , Veselin RaychevAffiliated withGoogle
  • , Fabien VigerAffiliated withGoogle

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Abstract

We show how to route on very large public transportation networks (up to half a billion arcs) with average query times of a few milliseconds. We take into account many realistic features like: traffic days, walking between stations, queries between geographic locations instead of a source and a target station, and multi-criteria cost functions. Our algorithm is based on two key observations: (1) many shortest paths share the same transfer pattern, i.e., the sequence of stations where a change of vehicle occurs; (2) direct connections without change of vehicle can be looked up quickly. We precompute the respective data; in practice, this can be done in time linear in the network size, at the expense of a small fraction of non-optimal results. We have accelerated public transportation routing on Google Maps with a system based on our ideas. We report experimental results for three data sets of various kinds and sizes.